Now what you are looking for are files with the extension .mdx, which are 3d models. You will see that there are lots of mdx files for units listed there, and you will also see that for every unit there is a portrait mdx file associated with it.
For example:
The arthas unit model is:
units\human\arthas\arthas.mdx
and the associated portrait is:
units\human\arthas\arthas_portrait.mdx
Now what you have to do is find the portrait that you want, and extract it into any folder on your hard drive. Then simply rename it to the name of the unit portrait you want it to show up for. Once this is done, then simply import that file into your map, making sure you put it in the exact same path that you got it from in war3.mpq.
Finally finding about some of the bots that are flooding the users online - bytespider apparently is a huge offender here - ignores robots.txt and comes in from a ton of different IPs
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.