Granny Squares - A New Beginning

A couple of years back, I crocheted my first attempt at a granny square, but never made any other squares after that..... until recently where I spent a Sunday learning the granny square from basics at a course arranged by one of the local night schools.

 

The middle red square was the first square to get a grasp of the basics before starting using multiple colors and we learned how to stitch the squares together with a needle. Wondering if I could use the above to create a pillow cushion cover, where the back is one big, or several small granny squares in the dark grey yarn?

Could actually be cool to take it a bit further one day and combine knitting and granny square crochting technique to make something like this.