is there a way to make custom decals and uload them to your xbox with an ar maxx or memory card?

I dont believe so but wait till someone else replys

well your car decals/templates are hash filenames that are in teh livery folder of the save so edit/resign/upload via Action replay try taht out, juremember that you should most likely keep backups of the save since all the decals of that profile could get deleted or corrupted and so on......