I'd have to agree with this fellow above me. I'd much rather download a zip file than have to use a downloader program to rip the images from a FHG.
How many galleries do you have in your members section? A zip file of sample pics for every single gallery should be the goal to shoot for. Around 15 pics each, and a bit larger in size than you currently offer. That'd be my only advice, as it seems to be what everyone else does.
If you do still need help with anything, I'd be happy to offer it in exchange for the occasional shout out on twitter with a link to my site / twitter. Let me know.
Good luck
