merge 2D layer on top of 3D surface

Is there a way to merge a 2D-image, (e.g. picture, map, design) on top of a 3D surface? In the way the surface will covered by the design, while the surface structure stays the same?

Yes - that is called planer mapping, although there will be stretching on the vertical parts of the mesh. For this reason UVs are spread out so the texture will map to all sides of a surface.
Unity doesn’t have this (afaik) but this can be accomplished in any 3D package with ease. blender is free.

Hi, thanx al lot, gonne give it a try.

Isn’t that what Decals are?

thnx, looks indeed like Decal.