Wolf & Moon: Looks good overall. The wolf could have been cut out more diligently - left side of the wolf as we see it has extra portion and right side fur is fuzzy. There was no attempt to deal with shadows, but it is not that necessary in this composition. Positive point is, if you were able to do this, you are capable of achieving much more provided you invest time and efforts.
Snake & Skull: The background looks more focused than the foreground. There is a clear light source in the sky, which casts a shadow at the entrance of the cave but there is no hint of shadows cast by Snake & Skull. Rest of the cave is dark, but there is supposedly a light source casting its light on the Snake+Skull+Rock - Nevertheless, that source should be casting shadows, especially under the body of snake, on its neck portion where shadow of the hood would be, etc. Also, the Skull and the Rock have an outline that need not be there? Snake cut out could have been better.
Not commenting on the Lion image.
Overall, you have skills and they have a potential to be honed further. Photoshopping is fun and we are all learners.