If you're talking about the textures for each of the items that Brawl has, you need to edit common3.pac.
Too be more specific you need to download both common3.pac and brawl box. Any version should work.
Put your common3.pac here
private/wii/app/rsbe/pf/system
Now to replace the texture and/or model.
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1. open brawl box
2. open common3.pac with brawlbox
3. extend the itmcommon.brres bar
4. find what you want to replace there.
5. right click and replace (or CTRL R)
