you need to make the blood have the same perspective as the ground. Same goes for the pictures (and a little bit of adjustment for the gun as well). As for the blood's realism, I think that you should edit the shape, like have it going in the cracks of the ground, raise the opacity on it. add a shadow on the picture, and brighten up the gun and increase the contrast on it. add a shadow for that as well. You might want to get rid of the tape because why would somebody tape a picture to the ground? lol um... and dont have the picture over the top of the gun, you might want it vice versa. have the gun on top of the picture (just a corner or something) after all of that, i think youd be well on your way to a nice photo manip