According to this answer on Judaism StackExchange regarding different rules for what kind of art is allowed, it states that:
There are differences between representation in relief (3 dimensions) and flat (2 dimensions), and between whether there is a possibility that idolatry might be involved or not e.g. when the representation is educative.
What's not clear to me from that is whether Ancient Egyptian-styled sunk-reliefs that were inwardly carved into walls (really only the outline of a flat 2D painting is indented usually) are considered to be 2 dimensional or 3 dimensional for the purposes of determining whether an artwork in that style is halachically permissible. Perhaps, I need to specify something that would be created in such a style, so I will say pictures of angels, and possibly humans as well as animals & nature.
Angels are an especially sensitive topic here because Shulchan Aruch (Yoreh De'ah 141:4) states that two-dimensional images of angels are permissible, however a 3D image might not be.
Now, I will give an example of the Egyptian style I was having in mind. This is one of the few pictures that doesn't seem to have any idolatrous elements in it (just a person - you can see the flat 2D art style, but its etched inwardly into the material to give it a feeling of sinking. I don't know if this would be 2D since the artwork is flat, or 3D because of the inwardness, despite it being relatively low sunk relief. Also this picture gives it an even stronger feeling of curving that would be presented, if any at all, because of the material its being carved on. Normally, you would quite literally just have a flat outline with a flat painting, but I can't find an example that might be acceptable here):
Assume that for the sake of the question, the sunk-relief would be colored like a regular 2D painting of this style (but all of it is done on a wall - I'm not sure if that would change whether something is considered 2D or 3D):