Truthfully Google Docs isn’t the most conducive for adding backgrounds or creating posters, cards, flyers, infographics or etc… There are two GAfE APPs which are easier to use for this purpose. The easiest Google Drive components for creating these items are a Google Drawing and Google Slide.
If one is in for a challenge it is possible to create a Google Doc with a pretty background. This method will come in handy if one is looking to create a fancy Title cover for their research project. What one has to do is insert a Google Drawing into the Doc. This will allow the creator to layer type over an image.