yellow8 offers version 1.1 of " 3ds homemenu extdatatool "Application for Nintendo 3DS, to install custom themes from the Home Menu.


How to import your own custom theme:


Place edited body_LZ.bin from Theme Customisation Tools in sd:\3ds\3ds_homemenu_extdatatool or wherever your theme folder is. If you have a custom BCSTM file (currently only possible to make with Brawlcustommusic database), rename it to BGM.bcstm and place it in the same folder. Then open 3ds_homemenu_extdatatool, enable theme cache and import theme cache from SD to ExtData. That's it. :P

Dev Units:

I wonder if Dev Units have access to themes, but anyway how to make it work:
Use SaveDataFiler to dump Theme ExtData which ID depends on your console's region, either 000002CC, 2CD and 2CE. Go to Config app, other settings and change Menu to Test Menu. Restart your 3DS, go to SaveDataFiler and reimport edited ExtData. Return to Home Menu with Config app.


Technically should work like Dev Units method, but you can't go to Test Menu. So it's quite problematic. :S


If you want to make Custom Theme work nicely, change your base theme to anything besides default theme beforehands. If you don't, your theme will disappear after you put your 3DS to sleep mode.