I use "Best Album" for showing off my images. Not sure whether it's customizable enough for your purposes, but it allows you to organize your images into different collections, and to add basic comments/titles.
I've got a few - Pad Folio, Padport, Collections, and Foliobook. Pad Folio is probably the best of the bunch, with Padport next. Collections is last, not because it's a bad program, but not as well suited as a portfolio as the others, I think.
If you have the Datacolor Spyder3 system, they now offer free tools for color calibrated photo display on your iPad. It takes minutes to do and does make a difference in how your images are displayed on the iPad. You have to load your images into your iPad Photo albums, then launch their iPad SpyderGallery app and view your images through their app.
It does not color calibrate the iPad like you can your computer. It just color corrects when viewing images inside their gallery app. But it does work and it offers a few features for watermarking and making your presentation look more professional.