- Good idea.
- Very un-realistic.
- Bad textures and skybox.
- Bad lighting.
- Use better texutres and skybox texture.
- Learn the entity light_environment.
- Take better screenshots with HUD off, to do that just sv_cheats 1 and cl_drawhud 0.
- To make it more realistic, add decals, props, etc.
- In YouTube you can find loads of tutorials on hammer editor. Watch them to learn more.