Added.
I have not added a way to upload your own files. However, I have added a way to define your own file name. All you have to do is upload your own file and point the boot settings to use that new file. The handling for colour and cpair commands are left just as text boxes. You need multiple changes, you just need to enter a new line and type. This leaves potential errors being left unto the users, but should be able to allow more people to make their own color schemes for the boot menu.
Useful links:
http://ipxe.org/cmd/colour
http://ipxe.org/cmd/cpair
of course, I should note, you can, I suppose, inject any ipxe code in these fields, however I doubt that will be much use to others as they’re stilled called only in their relevant functions (get_console/alt_console/host).