A series of icon sets of people and objects, both of which can be accessorized by the user, such as adding glasses (illustrated below). 

Finished with icon set 1 which is available in .svg and other formats (Pixabay) and is free for use under the Creative Commons License.

Below is icon set 1. Includes icons with lines and without, with background, with background shadow, and without. 

My mix-and-match idea is best illustrated by the pairs of glasses on the left. 

Below is an example of the mix-and-match idea. Glasses, backgrounds, and icons can have their coloring changed or resized.