Nice Redshoe!
The only advice I would have (since I do the same kind of half to full page graphics) is to get your file size down as much as possible. Compress, compress and then compress some more LOL. And chop up the image so it will load piece by piece. The surfer won't get as bored that way as opposed to having to wait for it all to load.
It's easy in photoshop, which I think you've already mentioned you use. Use the guides and make sure it's checked on "snap to guide". Chop it up in like 100x100 squares or whatever. Choose rect tool set it at a fixed size at 100x100 or the size you've chosen. Move the square to your first section, it will snap to it, cut, open new file, paste, save. Do it with all of them and then make a table and insert. Make sure to use
tags at the end of each <td> so there are no spaces.
Pardon the post if you already know this
If anyone else has an easier or different way to go about this, post please, I would be interested too.