Take rowan's advice.
Simple always works best. You want to impress the user with the content, not millions of ads.
Surfers won't even look at the ads even when they're right in their face. The attention goes right to the content. So you want to make the content as high quality as possible to really impress them. Both the thumbnails and the full sized images should be the best quality possible while not giving away too much and not chewing up too much BW either.
Then throw in one animated gif, or a big text link right below the content that basically says "For more pics like this come on inside!"
A little bit of unobtrusive text to build up the surfer's expectations and fantasy a little can help too.. but most surfers won't read it... so don't go all out .. one short paragraph max.
That's pretty much the formula for a gallery. Leave in some room to throw 3 recip links at the top .. and you're set to go.
You don't need a lot of design experience either .. this guy submits to me a lot and his galleries are plain and simple .. yet do the trick:
http://petiteteenager1.com/TGP/cheer...u/fivesub.html