Can decals printed on an inkjet printer be sealed with Future?
I think you would be better off using a spray clear lacquer on inkjet inks. They are water-soluble, and I think they would tend to run or bleed with Future. You may be able to airbrush Future in thin enough layers to prevent running, but I would experiment on some expendable images first.
Even lacquer causes them to bleed. I use Testors Glosscoat or Dullcoat, which are lacquer spray cans. I use two coats. The first is just misted on . When thoroughly dry I put on a second, heavy coat.
I have even used spray Polyurethane. The lacquer sprays causes a bit of a shrinkage, which means they want to curl and makes applying them to curves more difficult. The curling doesn’t affect applying to flat surfaces much, but if I put it on a really curved surface I tend to use the urethane. With the urethane I use same procedure, misting on first coat and then a heavy second one.