Ah alright I see.
What Loomis' illustrates as sort of.. an Egyptian collar if you will is actually two muscle groups, sort of, but cut-off in the delts (not quite sure why he cut it there).
In any case, the pecs (chest muscles) should be lowered down, they look a little too squished in there and don't appear to have an origin point.
The rib cage should be slightly narrower and straighter, if you look at a real skeleton you can see what I mean (it actually goes slightly outwards toward the end even, sort of like this: / \).
The part where the shoulders are I think you should create with full delts, not cut-off ones like in Loomis' illustrations (like I mentioned already).
The traps (muscles behind the neck that attach to the scapulas) should be a little more separated and distinct.
Here are a few fancy sketches I drew right now (it mainly has to do with muscles, so you can leave it for later):
With the pecs there are mainly just two heads, the clavicular and sternal (there's also a "coastal" head if you want to call it that which attaches to the rib cage, but it's not really important since you never see it; and there are I think another two muscles under the pec, but they're also kind of unimportant).
I also created a small image showing how it looks like when the arm is raised, as you can see the clavicular pec becomes much more pronounced (just wanted to include this for future reference).
With the traps there's not a lot to say, just wanted to show how they're connected. Same with the delts.
Hope this was of some help!
edit*
I just realised what you meant by 3/4 view; I for some reason had this in my mind that 3/4 is only like bird view in games, if you want to make it 3/4 it's absolutely fine. my bad