It shouldnt make any errors, because if that file is missing, the old mpq file (roc's background) will autodisplay in its place, ive done this a while ago with an mpq editor though, nice to see a program that does it for you... for less experienced people, Note: you should also include a link, to some backgrounds (extract all the game ones, and maybe add a few campaign ones....)
EDIT: Judgeing by program size, id say it already has them?
EDIT2: after testing it out, i realized, it disables battle.net play, and pretty much reverts the game back to how it was b4 the patch, rather than creating a new patch, the program should simply edit the old one, that way theres no room for error, and the user dosnt have to replace their files.... In this state i dont recomend aproval....