You have to make sure the mod is compatible with the version of the game that you're using. If you're playing 'vanilla' Necrodancer, ensure that the mod does not require the Amplified DLC. Likewise, if you have Necrodancer Amplified, the vanilla mods will crash your game.

This is because the game requires specific pixel dimensions for its graphical files, and those dimensions were changed between the vanilla game and Amplified: more armor types were added and an "on wire" effect was added, extending the dimensions of the player graphics. Several entities such as enemies also had additional frames added.

actually, i just learned that, joined thier discord (of the game) and well some artists accepted to add theses sprites to the mods pre amplified but thanks anyways