This will probably never get finished so I'll just link some good guides and useful mall resources here :P

1. Guide to Malling
http://www.neopets.com/~bugsy_lenny

2. Shopkeeping and Malling Guide.
http://www.neopets.com/~Anegil

3. Code your mall maps
http://www.image-maps.com/

3. CSS code text showing up in the marketplace? Dont like it?
http://www.neomallers.com/node/2050