Just made a sprite sheet, I could use some constructive criticism.

[Gors]

The basis of sprites being accepted to tSR relies in two big rules: It must be of high quality and it needs to be (mostly) game canonical. That is, your sheet does not qualify in both (it's both a splice and a rather simple edit of Mario and Mario has never been battle damaged like that status-wise).

Of course, there are many exceptions for those rules but your sheet is not an exception, hence why your work was not accepted.