Bonus photos - At the "Press Start" screen, quickly press Blue, Yellow, Orange(3), Blue(3), Yellow, Orange to unlock bonus photos. If you entered the code correctly, a message will appear.

"The End" song - Successfully complete Story mode to unlock "The End" song from Abbey Road.

Challenges - Successfully complete the indicated chapter in Story mode to unlock the corresponding challenge:

The Cavern '63: Chapter 1
The Ed Sullivan Show '64: Chapter 2
Shea Stadium '65: Chapter 3
Budokan '66: Chapter 4
Abbey Road '66-'67: Chapter 5
Abbey Road '67-'68: Chapter 6
Abbey Road '68-'69: Chapter 7
Apple Corps Rooftop: Chapter 8

Photos - Successfully complete the following tasks to unlock all 108 photos:

Get three stars on each song in Story mode to unlock a photo.

Get five stars on each song in Story mode to unlock a photo.

Successfully complete a chapter in Story mode with at least three stars on all songs to unlock a photo.

Successfully complete the following challenges with the indicated number of total stars to unlock more photos:
The Cavern '63: 20 stars
The Ed Sullivan Show '64: 20 stars
Shea Stadium '65: 25 stars
Budokan '66: 25 stars
Abbey Road '66-'67: 30 stars
Abbey Road '67-'68: 30 stars
Abbey Road '68-'69: 35 stars
Apple Corps Rooftop: 30 stars

Successfully complete Chapter 8 to unlock the final two secret photos.

Prizes - Get the indicated number of photos to unlock the corresponding secret prize in the "Prizes (Secrets)" gallery in Story mode:

The Beatles Christmas Record: 1 photo
Secret 2: 11 photos
Secret 3: 31 photos
Secret 4: 51 photos
Secret 5: 71 photos
Secret 6: 90 photos

Movies - Successfully complete the indicated task in Story mode to unlock the corresponding movie:

Intro movie: Begin Story mode.
Chapter 1 movie: Successfully complete Chapter 1.
Chapter 2 movie: Successfully complete Chapter 2.
Chapter 3 movie: Successfully complete Chapter 3.
Chapter 4 movie: Successfully complete Chapter 4.
Chapter 5 movie: Successfully complete Chapter 5.
Chapter 6 movie: Successfully complete Chapter 6.
Chapter 7 movie: Successfully complete Chapter 7.
Chapter 8 movie: Successfully complete Chapter 8.
Outtro movie: Successfully complete Story mode.

Instrument icon plates - Get the indicated number of trophies to unlock the corresponding instrument icon plate:

Silver: Unlock 15 trophies.
Gold: Unlock 30 trophies.
Platinum: Unlock 50 trophies.

Trophies - Successfully complete one of the following tasks to get a trophy:

A Little Help From My Friends (Bronze): Start a Story with a four player band.
All Together Now (Bronze): Get a Guitar, Bass and Drum unison bonus on the songs listed on the Trophies.
In Seconds Flat (Bronze): Maintain Beatlemania for 60 seconds.
Shake It Up, Baby! (Bronze): Use Beatlemania at least 5 times in a single song using either Bass or Guitar.
Eight Days a Week (Bronze): Get an 8x Band Multiplier.
Like a Million Suns (Bronze): Score 1,000,000 points in a single song.
Authenticity (Bronze): Finish any song as a Bassist with Lefty Mode turned on, hitting at least 50% of the notes.
How Could I Dance with Another? (Bronze): Score 100% playing I Saw Her Standing There on Expert Bass.
Day Tripper (Bronze): Start a new Story save file and reach the credits within 24 hours.
Let's Get Some Levels (Bronze): Calibrate your system for the optimal experience.
Elmore James Got Nothing on This (Bronze): Get 85% or better on all solos in The Beatles: Rock Band on Expert Guitar.
Sun, Sun, Sun Here it Comes (Bronze): Get a 350-note streak playing Here Comes The Sun on Guitar
That's It! You've Got It! (Bronze): Get a 350-note streak playing Hey Bulldog on Bass.
Goo Goo G'joob (Bronze): Get a 550-note streak playing I Am The Walrus on Drums.
Do Right By Me (Bronze): Get a 350-note streak playing Ticket To Ride on Guitar.
The Words You Long to Hear (Bronze): Earn a five-star rating for the songs on the Trophies screen as a Vocalist on Hard or Expert.
She Still Sings It with the Band (Bronze): Get all possible Double Fab ratings for every song with 2 vocal parts.
Liverpool Lads (Bronze): Play a song in The Cavern '63 in Story.
Really Big Show (Bronze): Play a song on The Ed Sullivan Show '64 in Story.
Stadium Superstars (Bronze): Play a song in Shea Stadium '65 in Story.
The Final Tour (Bronze): Play a song in Budokan '66 in Story.
In the Studio (Bronze): Play a song in Abbey Road, Studio 2 in Story.
Mr. K Will Challenge the World (Bronze): Finish all 8 Chapter Challenges.
Toppermost of the Peppermost (Bronze): Finish all 8 Chapter Challenges with full star ratings.
I Saw the Photograph (Bronze): Get your first Beatles photo.
The Teachers Who Taught Me WERE Cool (Bronze): Complete all the Beatle Beats.
Doing the Best That You Can! (Bronze): Complete all the Drum Lessons.
Gear Guitarist (Bronze): Earn a Guitar Career Score of 1,000,000.
Ace Bassist (Bronze): Earn a Bass Career score of 1,000,000.
Dazzling Drummer (Bronze): Earn a Drum Career score of 1,000,000.
Sensational Singers (Bronze): Earn a Vocal Harmonies Career score of 1,000,000.
I GOT BLISTERS ON MY FINGERS! (Silver): Score 100% notes hit on Helter Skelter playing Expert Drums.
Better Free Your Mind Instead (Silver): Earn Expert gold stars on the 4 songs listed on the Trophies screen.
No One's Frightened of Playing (Silver): Earn Expert gold stars on the 4 songs listed on the Trophies screen.
And the Band Begins to Play (Silver): Earn Expert gold stars on 4 songs listed on the Trophies screen.
Things That Money Just Can't Buy (Silver): Earn Expert gold stars on the 4 songs listed on the Trophies screen.
Still my Guitar Gently Weeps (Silver): Hit 100% of the notes in either of the solos in While My Guitar Gently Weeps on Expert Guitar.
What I Got I'll Give to You (Silver): Hit 100% of the notes in the solo of Can't Buy Me Love on Hard or Expert Guitar.
We Would Be So Happy, You and Me (Silver): Play Octopus's Garden on Expert Guitar, playing all hammer-ons and pull-offs without strumming.
Won't You Come Out to Play? (Silver): Play Dear Prudence on Expert Guitar, playing all hammer-ons and pull-offs without strumming.
Pick a Moon Dog (Silver): Play Dig a Pony on Expert Guitar, playing all hammer-ons and pull-offs without strumming.
All the Children Sing (Silver): Get all possible Triple Fab ratings for every song with 3 vocal parts.
Passed the Audition (Silver): Play all the songs on Apple Corps Rooftop '69 in Story.
All You Need is Love (Gold): Five-star every song in The Beatles: Rock Band
The Complete Anthology (Platinum): Wow! You've gotten all the Trophies in The Beatles: Rock Band.

Additionally, there are six secret trophies:

Don't Let Me Down (Bronze): You saved a bandmate from failing!
Oh Yeah, All Right! (Silver): Hit 100% of the notes in the solo of The End on Hard or Expert Guitar.
Are You Gonna Be In My Dreams? (Silver): Hit 100% of the notes in the solo of The End on Expert Drums.
In Penny Lane There Is A Barber (Bronze): Get half of the Beatles Photos.
The Love You Make (Bronze): Complete the Encore in Story.
Images of Broken Light (Silver): Get all the Beatles Photos.