I've had great results buying vinyl decals from local sign shops. Get the .jpg file you need off the internet or the sign shop may be able to find the image (file) you need. They can shrink the image or enlarge it as you require. Spray a little Windex on the area you're covering, peel the backing off the vinyl decal, position the decal as desired, then peel the front covering off the decal. Squeegee off excess Windex and let dry. I did this recently with a NASA decal as a test to see how well it works. I sprayed the decal with Krylon Flat Clear. It's an electric plane so fuel proofing is not an issue.

The water transfer decals are ok but I prefer buying vinyl decals from a sign shop. I'm always very satisfied with the results.