Changing the Backgrounds

[Rayfa]

Using the default screenpack of Mugen 1.0, and is wondering to how to change the backgrounds to everything?

[Odb718]

Depending on using winmugen or 1.0+ you'll check
http://mugenguild.com/forum/your-releases-1-0.359
or
http://mugenguild.com/forum/your-releases-older-mugen.309
and hit the grey button for screen pack. Download the one you think is cool and install it.
You'll need to edit the select.def to have your characters and stages.