One of the common problems when I am asked for feedback on art is the lack of variation. There is one stone tile, one grass tile, one tree and they are repeated again and again in a level.
The big advantage of doing vector art is the ease to create variations by rearranging the shapes that make up new object.

For this tutorial I picked a tree as an example of what you can do with detail and how to create some simple but effective variations. One can go from very simplistic / minimal to very complex and detailed and both have their uses. 

In general more detail and variation makes for a realistic look and feel.
 

Note: 

In the sample images I set the colours of the ground first and use the colour picker to assign the same colour to the trees.

  The more detail and variation you add to the tree to more interesting and realistic it will turn out.    Note: I like to create 'clusters' of objects - eg. take a few leaf objects  and group the in a bunch - pointing different directions. Duplicate the group to place a lot of leaves a lot quicker. By mirroring, rotating, scaling and overlapping the groups they will look less like the same object.    I hope you enjoyed this. It's a great subject to play with and create unique trees and variations of trees and other vegetation quickly and easily.   

  Here are some free trees from the tutorial above. download the zip archive  (containing 5 trees as png images and a svg file)   

  I continued to play with the trees and made some more detailed objects and variations as well as some odd shapes to make trees off. Check it out on my blog '2Dgameartforprogrammers'.