Here is an image I am working on. It is a quick one, but I would like to spice it up.
What is the best way to blend cutouts nicely in a scene. I am happy with the background trees so I think I might try cutouts for all the trees. Also what is a good way to paint, in PS, flowers on the grass? I want to paint in the perspective. I saw a video once, but I couldn’t find it.
Cut out
I ended up updating the image with cutouts. I am still interested in painting flowers on the grass.
First, that’s a nice image, although I think the vignetting is a bit over done.
As for the flowers you could use a custom brush in photoshop.
I think a few flesh eating zombies would give it some scale. You could add regular humans if you fixed the lighting 
nice but I dont think the sky is doing it any favours
Sky
What is wrong with the lighting. except the lack of hard shadows? I uses an HDRi as my light source. I started adding people, but my library is weak on 3d people and I don’t like to use cutouts… mostly because I am not good at blending them into the scene.
Are you going for a sunny afternoon like the sky somewhat indicates, or are you going for sun peeking out of the clouds after a nasty thunderstorm, which is what it looks like? It’s dreary and dreadfully dark.