Most of my icons are of video games, but just about everything is fair game when it comes down to me, boredom, and a graphics program.
My terms are pretty simple:
1. Do not claim you made my icons yourself. This is really the only rule that is actually a rule. I can't really enforce it, but it goes without saying that if I see this going on, I'm going to be less than thrilled. My icons aren't the end-all-be-all of icons, I realize, but I do put a certain degree of effort into them. So please don't.
2. Credit is nice, but optional. It makes me happy to see it, but I will not hunt you to the ends of the earth if you don't put it there. I know people sometimes forget, or save something and forget where it came from later, etc. etc., so really, it's not a big deal. It's totally up to what you feel like doing.
3. Same goes for comments. Entirely optional. I do like knowing when my icons are appreciated, but again, it's up to you. On the internet I tend to be a bucket full of shyness stored in a shy container and locked up in a shy basement somewhere, so it'd be hypocritical of me to DEMAND COMMENTZ. So don't worry about it.
4. I don't take requests. Mostly because my bursts of inspiration are sporadic and fickle, not because I don't like making icons for people. It just wouldn't be fair for me to agree to make such-and-such icon for someone and then end up... not doing it, for whatever reason. I do take suggestions, though. For example, "Hey, veridium_falcon, do you think you might make some icons of such-and-such sometime?" Why yes, I might just do that, thank you for the suggestion! Etc.
If you've made it to the end of my awkward profile-writing: Congratulations! You may now want to go look at some icons!