you can

Use my art as an icon/header
Use my art on your sidebar/as a background/as a desktop wallpaper
Use my art in edits, AMVs, MEPs, and similar. (add gradients, change sat., edit bg, add text, other aesthetic stuff).
Print my art on posters, shirts, journals, etc. for personal use only.
All of the above is allowed as long as you credit and link back to either my Twitter or Tumblr.

you cannot

REPOST MY ART. At all. Ever. Don't do it.*
Repost my art on Facebook/Pinterest/WeHeartIt etc.**
Tag my original art as kin/id/me, or art that has "Don't tag as kin" in the description.
Trace my pictures/Edit them with other characters, and similar.
Redistribute my art for commercial use/Selling any of my art in general ever.
Claim my art as your own.
Heavily reference my art. Referencing is always ok, very heavily/heavily referencing is not.

*I ONLY allow this if it's an edit and you credit & link back.
**These I won't allow even if it's an edit, you credit, and you link back. If I see this, I'll report you.