suggestions:
1) improve shadows, if light source from top, the shadows should be alittle bit..
the 'houses' look like floating now
2) add people, since it is a street
3) add a dark to light color for the floor too

Nicely done mixture of day and night. Original concept!

Nice Idea adding the clouds/stars blend.

Very common idea but not bad. GL!

This just looks like the contest source overlaid on top of an image.

hmm... quite similar to "mosiac girl"....

suggest you mask out the blue background, fill with white (or other color)... or a gradient fill
to make it stand out...

quite nice, actually