If you want to use oUF_Dispellable for this, here is some
sample code how to use backdrops with it. However, if the class cannot dispel at all (DKs, rogues, warriors), oUF_Dispellable will completely disable itself. While I don't understand why you want to highlight the whole frame based on a debuff type that is undispellable by the player, you could use a check like IsElementEnabled('Dispellable') and then use oUF's PostUpdateIcon to get the debuff type.
If you dislike this, oUF_Dispellable uses LibPlayerSpells-1.0 to fetch the list of possible dispel spells for the player's class. Feel free to use oUF_Dispellable's code if you want to use this approach but code your own DebuffHighlight element. If you consider the 616 KB static memory use of LPS a waste, you can just use it to build you own table with dispel spell IDs. The dispels are based on spec and honor talents, some are self-dispels only and for warlocks some depend on the currently summoned demon. Keep in mind that LPS does not differentiate between pet and player as a spell source, you have to read the code comments for those special cases for the warlock class.