I agree the answer is yes.  I have done a few and entered them in art shows where there is a mix of collage and dioramas.

Thanks for response and good advice.

Michael Wilson said:

It can be as long as it doesn't turn into a Diorama. What I mean by that is it should be done contextually and not too figurative. Give the viewer a chance to interpret without being literal. I guess that means abstract it a bit.

Hey there Peter,

Sorry for the late response, i just signed on from a long absence. It seems to me that all dioramas are assemblages, but not all assemblages are dioramas. So, in short, yes, dioramas are assemblages. 

The thing about which one tips the scale toward art would likely tip the scale away from art if it is too didactic. 

Michael Wilson brings up a good point, that if it is "abstracted" in some way, as in leaving things out, allowing room for interpretation or raising questions or straddling boundaries, then it is more weighted toward the stuff of art.

Check out the 1990s model work of Michael Ashkin:

http://www.michaelashkin.com/model.php?p=1.1.3.1

Or check out the Chambers of Charles Matton:

https://charlesmatton.com/boite--.html

Both these artists straddle the diorama/art line in very interesting ways.

I'd say, go for it. Own it. Make it work!

I hope this is helpful.