This isn't a total site construction solution, but SlideShow Director and
SlideShow Pro (http://slideshowpro.net/
) are pretty great
apps for self-maintaining your portfolio on whatever site you end up with.
SlideShow Director gets installed on your host's server and SlideShow
Pro is on your computer, with a full Flash CS plug-in for detailed
tweaking. It's what I use, and only to shallow degrees, on www.artofpendeton.com
to create and
maintain my galleries. I put my own watermarks on each piece originally, but the
latest update has a watermark feature that covers all your content uniformly.
It's not free, but it's a really good price for the utility you ultimately get.
It was originally designed for photographers, for just the purposes you're
looking for, it sounds like.