Plus 1, and some suggestions....
They look ok, but you wanted some critique, so here goes.
When you back rivet, be sure to hold the set perpendicular to the work. It's hard to tell from the photo, but it looks to me like some of the rivets are smushed to one side a little, indicating the back rivet set was slightly angled when you squeezed the trigger.
First, they look fine and as long as the manufactured heads look good you should build on IMHO.
Some do look a little canted to one side, and I had the same problem. If memory serves, I tried to correct this by either applying a bit more firm pressure with my thumb and fingers holding the back rivet frame to ensure that a) it was flush and therefore perpendicular to the riveting surface and the rivet shank, and b) that the back rivet set would not move when I started riveting.
I may have even applied some pressure with my other hand on the top of the rivet gun instead of holding the back rivet set, but I think I actually did the former method by holding the rivet set with my left hand and the gun with my right.
Then there is the question of which back rivet set you are using - i.e. from which tool manufacturer? One company produces a rather large diameter one that many others have reported having problems with while trying to center the back rivet set over the rivet shank. This is because the diameter of the frame is too large, and contacts the vertical part of the stiffener. Other manufacturers make a slightly smaller diameter one that fits better on the stiffener, and therefore also centers better over the rivet shank, reducing the tendancy to cant the rivet to one side or the other.
Perhaps the most accurate reason I found for the slight canting of the shop heads was that my arms and hands were not kept close to my body and to the centerline of the rivet gun. In other words, every time I rivet I try to place my hands, arms and eyes in a position that is as close to the centerline of the rivet gun as possible. I think when you start getting your arms further away from your body that there is a tendency for the gun to lean back toward your body when you start riveting, and this is the reason why the canting occurs.
Keep two hands on the gun/rivet set-don't try to rivet with one hand and hold the skin open with the other - ask me how I know! Go slow with the rivet gun, making sure that the back rivet stays perpendicular and does not slide. - Easier said than done sometimes, but those are my suggestions.