Cheap-o that I am, I found a way to do inkjet decals with white areas. It does require a little patience and, depending on the decal, a steady hand. All it boils down to is this: print a reversed version of your decal on clear decal paper, clearcoat, and then brush paint the white and lighter colored areas with Testor's flat white. Let dry and then simply apply the decal paint side down. Here's a few I did this way using a ten-year-old 50 dollar HP printer...
The Pennzoil decal is from a kit sheet but the Frankenstein image was done using the method described.
These decals were done the same way except they were painted with decanted Testor's one-coat Inca gold...didn't even clearcoat 'em.