The fireworks model shows up as a question mark bag instead of a box of fireworks.

There is a missing reference to one of the fireworks models. Once the reference is added you will be able to see the fireworks model. You'll need an archive app that supports JAR files. If you don't have one you can download and install 7zip.

1. Close all running copies of Wurm.
2. Navigate to your WurmLauncher\packs folder. If you can't find it, open Steam, find the Wurm Unlimited listing in your library, right click, Manage, Browse local files. Go into WurmLauncher, packs.
3. Right click graphics.jar and Open with your archive manager or 7zip File Manager.
4. Scroll down to find the mappings.txt file. Open it.
5. Add this line model.fireworks.wurm.birchwood = pottery/potterf.wom as a new line anywhere in the file. What I did was search “fireworks” and put it in with the other lines concerning fireworks models.
6. Menu option File, Save (or typically CTRL-S). Close the text editor to trigger an update.
7. When the popup asks select Update to write the changes to the graphics.jar file.

You should now be able to see the fireworks box model.

NOTE: If you get “file in use” errors when updating the files, it is because a copy of Wurm Unlimited is stuck running in the background. Use Task Manager (CTRL-ALT-DEL) to close all copies of Wurm Client, or reboot to fix the issue. Then do the edit to ensure it saves.

NOTE: If a GM creates a firework from a non-standard wood type, it will show up as a bag. The fix for this is to add a new line for model.fireworks.<woodtype>, for example, model.fireworks.oleanderwood. You can find the model name by binding action 185 (get info) to a key and using it on the firework.

I was able to do it in Linux Mint. Use your built-in archive manager in place of 7zip. The procedure is pretty much the same.