MCreator issue tracker has been migrated to GitHub.
Existing tickets have been migrated to GitHub. Please open new tickets on the GitHub tracker instead. If you do not have a GitHub account, all feature requests and bug reports from forums are still considered and checked by the maintainers.
Update to MCreator 1.9.0.
For the textures, make sure their dimensions are 16x16 or 32x32, ... 1024x1024, ... or other combination of valid square sizes for Minecraft.