Can you post a picture of it so we can offer specific ideas? With it so large, you can do various motifs in different sections.
I really understand your hesitation. I procrastinated long and hard before quilting my sister's LC quilt because I wanted it to turn out very well, but I lacked skill. However, I wanted to put things in it that would make her smile and would enhance the theme. The theme was love of horses. (It also helps that she lives in a log cabin in Kentucky!)
In my layout, I had a lot of negative space, so I planned one motif (horse head I free-handed on paper till it was right, then cut it out and then made a template, surrounded by a circle made from a paper plate)---for all of those matching spaces. I also free-motioned a rope/lasso/loop-de-loop design, plus some channel stitching, big horse shoes, etc.
Use this quilt as an opportunity to improve your skills. Don't stay stagnant. You will get more and more confident. As the Quilting Marine says, "it's only fabric and it's only thread." Do one section at a time, and stop when you get tired or flustered.