The tag alias #65793 3d_background -> 3d_(artwork) is pending approval.
Reason: This tag seems superfluous, given it's not being used as intended and it's intention seems a bit questionable. The wiki says it shouldn't be applied to fully 3D posts, but as can be seen, it's applied to a significant number of such posts, making it little different.
It's intended to be used on posts that have a 3D background but 2D characters, however a more general "mixed 2D/3D" tag would be more appropriate for that as it could also handle backgrounds that are a mix of 2D/3D, characters that are a mix of 2D/3D, or 2D backgrounds with 3D character, without needing separate tags that are prone to misuse.
Given how much 3d_background is mistagged, and the need for a better alternative, aliasing to 3d_(artwork) is the best it can be aliased to without causing mistags (if the background is 3D, at least part of the image is 3D and thus 3d_(artwork) would apply).