Tables don't affect loading times (no more than any other form of page structure) - they are just interpreted text really. I've used them on all the sites I've made since I learnt a bit more about HTML awhile ago, and never looked back. Only danger in using them is that some browsers don't like a lot of nested tables, it can lead to unforseen conseqeuences.
For your artwork, if I were you, I would produce thumbnails and link to larger files on your server. Make the thumbnails large enough for the user to see what the images are. For the larger version of the images, don't make them too large. I use (as a rule of thumb) 600 width > the relative height - since this is suitable for a variety of resolutions.
If possible, choose web safe colours. If your user has a low colour setting on their computer - and you are not using web safe colours - the browser will replace your chosen colours with colours nearest to them (within the web-safe framework).
I hope this helps, good luck!