When compositing images together, look carefully and make sure that they all have the same level of noise. If some images are noisier than others, your composition will look off and distract the viewer.
Try matching all your images to the noisiest image. Or you can also try adding a “noise layer” on top of all your other layers.
To do so, create a new layer, fill it with white, and go to Filters > Filter Gallery > Texture > Grain. Set the Grain Type to Soft and adjust the level of noise that you want. Set this layer to multiply, and bring the opacity down accordingly.
This layer will add noise that will affect all pieces, allowing for a more cohesive composition.