There is a tool here that you can use to convert your photo to an image of the appropriate size (96 by 96). The site represents many many hours of tuning to help non-technical people, so they’ve done a far better job of it than I could do.
Select “Custom” in step 2, and choose 96.
Use “Good” in step 4. You can use the other settings, but the better the quality, the bigger the file will be and we have a 12k limit on image file size. To be honest, I think “Best” will work fine, but “Good” is your safest bet. If you do try “Best”, it’s simple enough to right click the image they make for you and check the properties. If it’s bigger than 12k, use your browser’s back button to try again.
I will relay any discussion here to the ShrinkPicture people so feel free to discuss trouble or suggest improvements if you’d like.