Greatcoat is fine, and should be worn most of the time. But on his backpack, he has a cover that is covering his greatcoat/blanket roll.
I do not think that there are any good references for these.
About the blankets on the back of the pack.. I am not sure. You aren't supposed to carry them there. However, there are drawings depicting people wearing something on their backpack, even though they are wearing their greatcoats.
Now, the question is.... Is that just the drawer trying to make the picture more interesting, or did they really carry the blanket (Or a 2nd greatcoat??) on the back?
I can not be sure about that, because the same guy has drawn pictures of soldiers with both something rolled up on their backpack, and with nothing rolled up.
Maybe different regiments had a different habit of carrying stuff, and some regiments did not obey the orders as much as others. I can not tell.
Another idea I had is that they could have put the "sleeping bag" that was issued to some troops on the backpack. It was officially allowed to be put on top of the pack. People generally did not do that though, because it was made out of linen and it soaks water and gets heavy in rain.
However, just not putting anything on your backpack is the safer and more accurate choice. It also makes your backpack look more alive, because if you stuff everything inside, instead of letting it hang outside, it all of the sudden looks like it should. A huge bulky bag made out of cowfur...
