My pictures too were the standard Walmart sized ones. I later regretted not printing them on my computer cuz it would've been easier to put together in my evidence package.
So, I separated out mine by month of the year starting with most recent. Then, I numbered each picture for each month from 1 to how man. Each month had its own separate numbers beginning from 1 to X. I am very bad with explanation but I will try not to confuse you here. On MS Word I put the month of the year and under each month I put the Picture numbers and typed up a small explanation after which I printed and folded the pictures into that sheet with an elastic band. And I was being myself with the explanations and headings. Not too complicated or professional will proper spelling and grammar, etc.
Example:
December 2009: Xmas with the Jacks'
1-5: Sponsor and PA at Jack's house dancing with Sponsor's mother Jane
5-8: Sponsor and brother James preparing cake for mother's surprise party
9-10: Sponsor doing what he does best at family party, sleep.
And so on and so forth. Be sure to do it in a way that if the IO were you question you about a certain picture, you have included a very simple explanation that you will remember for future reference at your interview, if asked for one.
If you are doing the computer printed pics, try to make them as visible as possible .. so maybe 2 pics per page .... number the pics and write an explanation at the bottom of each pic. Again, I had the event at the top of the page followed by pic which I called IMG01 followed by a brief explanation. Oh, and black and white printing does a great job too. Saves a lot on the ink.
Mind you, I have created a kick ass pile of evidence (any and everything I could think of about our relationship) and at my interview the IO looked at nothing. Instead, he handed back to me everything since the application was submitted with the present evidence I'd walked with. So, I walked out of the interview room with my hands full to my chin with sad thoughts of how terrible I felt for killing a few trees preparring all that supporting evidence.
I SCORED IN THE INTERVIEW TOO!
Good luck