Things I would say would be: (in addition to the op)
- Animated GIFs (any if not lots)
- Massive Images (as in 100's of kb in size)
- Thumbnails (like fake where it is the full image just specified at a smaller size*)
- Background images that make text hard to read
- Bad colour usage (dark on dark or light on light etc)
- Non-resizeable text
Can't think of any others atm... :P
* Just say an 800x600px image shrunk down to 200x150px instead of being recreated at that size (if you get what I mean)