So this is my first Critique of someone work. And I have to say, you got the Color Correction of the FG rock to your BG matching pretty dam good. However the scale of the FG rocks seems to be off. And the only reason I say that, is because of the Trees that are in that original element you took the rock from. Yes you could argue they are bushes..but they feel like trees. 2nd..the lighting..look at the bg trees in the Landscape plate, specifically the tree along the water's edge on the right. See there is a distinct high light and shadow side. Same with the rocks on the right as well. The Foreground rocks do not reflect this lighting. This looks flat and top lit. Usually looking at Trees will give you the first indication of where the light should be coming from. Also the horizon line of this FG element doesn't seem to match. Cause you have the horizon line of the plate sent to almost middle..and this bridge is below the horizon line. So why can we see under the bridge? We'd see very little of the top of the bridge. This bridge and rocks almost feel Worms eye view..The Clouds. I see you kept the original clouds in, and just added another set of clouds over it with a transparency. While this is a valid and nothing wrong with it, due to the 8 bit image source. The tone from highlights to darkness looks clipped when done this way. if you got rid of the cloud above the mountain that's just to the right of center, this would be resolved. Unfortunately that one little clouds is giving the game away. Also I would have done a gradation on a layer mask from top to bottom, making the top slightly more opaque than you have now, and as it goes to the horizon, it would feather off to more transparency. This would mimic what your original Landscape plate is doing. Darker at the top..lighter toward the horizon. Your FG element..pretty much the same lighting comment as your added rocks, with an addition...that green is a bit satuated. I’d tone that down a bit and darken. Water edge line seems blurry or soft and would be slightly darker than the sky. Also don't think the mirroring of the mountain on the left is working.