This is a very good first build, particularly the carving. I do have some suggestions. First the lock panels need some work. Leave the back with the beaver tails pretty much as they are but slim down the panels at the top and bottom of the lock. 1/8" is thick enough. Next, the lock panel in front of the lock is WAY too big. It should be no longer than the portion of the lock panel behind the rear of the lock, and it is too thick. Again take the top approach down to about 1/8" before you start your transition to the front curve. I wouldn't start the top of the lock panel moulding any further than 1/4" forward of the pan/bolster. In other words slim the front of the lock panel way down. Of course don't shorten up the front of the lock panel if you don't have the wood to shorten the front of the sideplate panel to match. The front and back of both panels need to seem to line up when viewed from the top or bottom. The actual profile of the panels can vary a little as no one would notice. This can be useful in leaving an even amount of wood around the side plate.
Next, the lock needs to be finished. The plate and cock should be filed and polished. Also, it looks like the lock may be set at little deep. That is fine as you build the rifle, but as you finish is up, it should be taken down level with the bottom of the lock plate bevel using a plane and mill file. The thickness of the lock and sideplate panels should match.
Third, the tang carving looks a little high/heavy. The raised carving should usually only be about 1/32" high. You can take it down a bit, if necessary, using a mill file. Also, I think some type of modeling is in order to lighten up the foliage.