BTW, just to make it clear how ambiguous your question is.
If you used a 4MP camera and saved your pictures as JPEGS you'd be able to get about 1500 pictures on a 2GB stick. if you used a 22MP camera and saved them as RAW you could get about 25 pictures.
So for pictures, somewhere between 25 adn1500
For MP3s
If you have lots of 1minutes tracks at very low quality, you could probably get about 2000 tracks on 2GB... if you wanted to put Green Carnation's Light of Day, Day of Darkness at very high quality, probably about 1 track.
So for MP3's, somewhere between 1 and 2000.