Looks good to me... although I am not sure about the guy off on the one side. He looks like he got frozen and then tipped over. But as you said, it isn't finished.
According to the references I have the shells for the short 7.5cm (the L/24 barrel) were about half the size of the 7.5cm shells for the long barrels. The shells you have appear to be for the long barrel as the others would be about half as long and didn't neck down like the ones you have. If you want I can send you copy of what I have so that you can see what I am talking about.
The diorama is representing the invasion of poland.
The beige guy is a polish officer and is being questioned by soldiers, the 2 dudes on the ground (LOL) they aren't finished yet, no worries as they will be completely erect when done.I was trying to depict a normal operations type scene that would be typical during the battle.
The shells I agree you are right, I'll try to fix it when I get back to it someday,right now I'm just really into aircraft.
I don't want to work on anything without the proper attitude as it reflects in the work.
I don't want you to think I am pushing... I just tend see comments like yours and to ask myself about it. Then have to look it up and to pass it along.
My feeling is that as long as you are happy with the diorama, model, etc. then all is well with the world. Paint it in Nascar colors (have seen it done with Panthers... actually looks pretty good) or pink... I will just enjoy the show.
However, I do like your muffler colors... you know it has been used but not to the extent that some people show. I don't think you should give up on dioramas, this one is looking good and when you get around to finishing it will be well worth the effort.
I think you're too hard on yourself, I think you've got a great little dio going there. Someone else mentioned your figures, and I will second it, that was actually what caught my eye first.
Since you say that it's a work in progress, may I offer one suggestion? If it's a scene from the invasion of Poland in '39, you might want to add the white crosses the Wehrmacht used then as their recognition markings (later replaced by the more familiar black and white Balkenkreuz). But I don't want to be a rivet Nazi, as appropriate to the dio subject as that might be :
I like your groundwork, too, and the way your building ruins have come out.
Sometimes giving it a rest will do wonders for you!
As our own worse critic we always eye what we know is wrong right away, and to us it is glaring!
I hear you about the summer tasks at hand, but don't be discouraged and always do a bit at the bench as time allows.
LOL! Yes keep going. You are off to a great start so make it a greaat finish. Yes you are correct about the ammo. It appears to be Panther ammo? It is a very nice piece and I for one will be alarmed if you do not post pics when your attitude allows to complete such a nice piece. C'mon brother!