Thanks for the rundown! I really appreciate it. I was just looking over the TF2 website and found my way to the Steam Workshop! Awesome that you can make stuff for people to use in TF2! Is it totally free or do people make money off of their contributions?
If Valve really likes your item, it'll go in the Mann-Co store and you get a cut of the profits from all sales of that item. I don't recall the exact figure at the moment, but the makers of the first round of non-Valve items made tens of thousands of dollars.
Also, if you make a map that gets added through an official update, people can buy "stamps" in the store that also give money to the map maker(s), and can be attached to a special hat that will show particle effects when you're playing on a map you've supported.