Of course let google index them. Use keywords in the meta title and description, and if no text at all on gallery use same keywords for pic alt tags etc.
Have all your galleries linked from your sites index page, via a gallery page or something, use same keywords as above for link anchor text or pic tags if using thumbs, and add sitemap xml to google webmaster tools.
When submitting to TGP's use same keywords as in title etc for your gallery description on the TGP's, same or nearly same for all TGP's.
When the traffic has died from all the crap waste of fucking effort TGP's that charge for a shitty listing (thehun.net is only one left worth submitting to, and free), sit back and enjoy free targeted traffic for your keywords from google and others.
Manipulating google is so much fun and profitable
