You can share your custom decals on  Open Horizon Booru

1. Take screenshot of your decal ingame
2. Upload your decal zip to https://catbox.moe/ for example: https://files.catbox.moe/st31e2.zip
3. Add post to the booru with a link to the uploaded file in the Source field

Decal creating guide: How-to-create-custom-decals

If you have problems with posting or just feel lazy to create an account, you can send your mods me and I’ll post it