I promised a few B+BRoomers I'd make this guide, and since it's one of the most asked questions, I'd figure I'd present this guide on how to swap vBrawl stage textures into Brawl+ stages. Obviously this does not cover stuff like Rain/Snow or things that are imported from other stages (like Shadow Moses lights onto Battlefield etc), but that should be easily adjusted for those that make those types of stages.
First step is to get BrawlBox. If you don't have it, download it here and extract it to a convenient place.
Next is to open BrawlBox ("BrawlBox.exe"). When it's open, go to File -> Open, and find your vBrawl stage texture. After that, open another instance of BrawlBox, and in the second one, go to File -> Open, click "My Computer", double click your SD card (where Brawl+ is installed), then "private", "wii", "app", "RSBE", "pf", "stage" and finally "melee". Note: if your vBrawl stage texture says "STGFINAL" in the first BrawlBox, you have to open "STGFINAL.pac" from your SD card in the second BrawlBox.
It should look like this: http://i41.tinypic.com/v2z537.png (the left should be the vBrawl texture pac, the right should be the Brawl+ stage pac)
In the first BrawlBox (the vBrawl stage texture), go down to "TextureData[0]", right click and hit "Export".
A save dialog will appear. Save it where you can remember it. Click "Save".
In the second BrawlBox (the Brawl+ stage), go down to "TextureData[0]", right click and hit "Replace".
An "open" dialog will appear. Find where you saved "TextureData[0].brres", and open it.
After that, hit File -> Save...
Close both BrawlBox windows. Your Brawl+ stage should have textures again!
First step is to get BrawlBox. If you don't have it, download it here and extract it to a convenient place.
Next is to open BrawlBox ("BrawlBox.exe"). When it's open, go to File -> Open, and find your vBrawl stage texture. After that, open another instance of BrawlBox, and in the second one, go to File -> Open, click "My Computer", double click your SD card (where Brawl+ is installed), then "private", "wii", "app", "RSBE", "pf", "stage" and finally "melee". Note: if your vBrawl stage texture says "STGFINAL" in the first BrawlBox, you have to open "STGFINAL.pac" from your SD card in the second BrawlBox.
It should look like this: http://i41.tinypic.com/v2z537.png (the left should be the vBrawl texture pac, the right should be the Brawl+ stage pac)
In the first BrawlBox (the vBrawl stage texture), go down to "TextureData[0]", right click and hit "Export".
A save dialog will appear. Save it where you can remember it. Click "Save".
In the second BrawlBox (the Brawl+ stage), go down to "TextureData[0]", right click and hit "Replace".
An "open" dialog will appear. Find where you saved "TextureData[0].brres", and open it.
After that, hit File -> Save...
Close both BrawlBox windows. Your Brawl+ stage should have textures again!