I see a ton of gallery submitters these days submitting galleries with poor thumbs. There is no color/contrast/saturation adjustments, photos aren't sharpened and the framing is horrible. If you don't know how, you should probably learn how to use Photoshop just to do this task alone. You will notice a drastic improvement for an extra 2 mins of your time.
Not only will you help your CTR ratio improve via the MGP/TGP page, but you will also convince more surfers to bookmark the TGP/MGP page...thus bringing you more traffic in the long run.
If you don't do this already, you'll see a huge difference when you put the extra time into it. I personally adjust every photo by hand including thumbs and full sized images... I can honestly say that this may play a large part in my above average conversions.
