TL;DR version: You can use my art as your avatar/icon with credit. However commissioned/gift artworks are off the list.
No reposting without permission in general. Even if you credit/link.
If you had permission in the past to repost my works, you can still keep the old posts but not repost new ones anymore.
Clarification about commissioned/gift art:
By default, please refrain from using/reposting commissioned/gift artworks. Unless the client/receipient is okay with it.
Exception: commissioned artworks meant for promotional materials (CDs, videos, banners…etc) are okay as long as you’re not using it with ill intent.