As a free site builder, I prefer sponsors that just take their large raw photos, watermark them, and zip 'em up. Don't bother with creating thumbs. We all build using a variety of ever-changing thumbs sizes. Any real builder/submitter has a variety of image tools at his/her disposable for re-sizing, thumbing, and general tweaking. Larger is better because I can make them smaller, but I can't make them bigger without fucking them up.
Also, give us zips of 20-30 pics. A lot of sponsors hand out sets of 15, but that means that we free siters have to use two separate photo sets to build a single site.
BTW, thanks for asking our opinions first. It says a lot about you and your program.
