My apologies in advance if anything I am about to say is something that you already know.
For people who promote via gallery building for tgp's, or via free sites for link lists, then we need content zips that have 20 pics per set.
Most tgp's (ie Pichunter) will let you make a gallery with 15pics minimum. I generally use 16, because that is what one of my partner accounts likes, and I like him to list me.
People who build for link lists like Link O Rama, Penis Bot, etc, need 20 pics. Sponsor that throw in a few extra so that we can pick and choose are always well appreciated.
Both groups of people need the pics to be in a series, or from the same set, in other words. Most places won't list you with mixed content from different shoots.
Speaking of pics, you might want to get a watermark on yours. Speaking as an affiliate, I despise when sponsors put huge watermarks on pictures that make it impossible for me to make decent hand cropped thumbs. But there is nothing wrong with...and I expect...to see a smallish watermark on the pictures. Leaving it off is missing out on a branding opportunity, imho.
There are tons and tons of things you can get into as you build your affiliate program. Were it me, I'd pick one tool, and start with it. Refine it with feedback from your affiliates, then move on to the next one.
Trying to do everything at once...especially if you are not coming from a affiliate background...can be hard to do.
I hope that I explained that clearly. Hit me up with any questions.