How to add background images to blocks? How to upload background images to blocks individually ? 

Is there any contributed modules available uploading background images to blocks?
Try the Background Images Formatter module

This module provides an image formatter who allows you to set an image in background of a div.
The images are from a field of an entity and not from a configuration page or sth else, so it's very easy to setup and manage.

This can be done using Views. Create a block, select the &quot;Background Image&quot; formatter for your image field, save, place the block, boom, you're done.