Hi there, welcome to PixelDam

As far as pixeling techniques, you should really go through this FAQ and follow the links to the tutorial websites.

Some tips from me:

1. work out a rough sketch as a basic idea. See if everything fits, etc.

2. collect a bunch of good pictures of your scene as a reference for details, colors, objects

3. see if others have made a similar project and learn from them (mind you: not copying or stealing art) or even see if you can do better

4. make a screenshot of the block and make that your project 'background' (do not include in your submission though) in a sub layer if you work with photoshop

5. you can show us work-in-progress images to get early feedback

Good luck

You could go for something that few people have done: transport or religious.

I hope to make some fun Italian stuff like deThch

Else will need patience and don't lose faith if your first project isn't great, than next will be better

I find that regardless of your concept and idea making your block fit into the hood you picked makes a huge difference. For example if you have grass in your block use the greens on the hood base. Incorporating the colors from the sidewalks also help a great deal. Also, the mood of the hood itself is important. For example, a historical, moody project in Neon Islands does not easily fit well.
Remember, your project is NOT a stand-alone piece, its part of the hood therefore integrate.
Additionally, once you choose a specific plot, check the surrounding pieces and use them to help yours. For example if your plot is next to a cemetary, consider placing a single ghost or a zombie in your project.
Be creative, add life and little scenes and everything possible to create interest.

Thank you, Jalonso. Those are very valuable tips and pointers.