Accompaniment patterns are a quick solution to take a simple compositional idea and flesh it out into a fully realized composition. However, a good arranger/composer doesn’t just use “stock” patterns, they pay attention to the melody, form, and lyrics (if there are any) when deciding upon the correct accompaniment.
Take your theme and variations with chords and add in some of the “stock” accompaniment patterns. Don’t forget to pay attention to your melody and lyrics (if applicable) when making accompaniment decisions!
Remember, it’s ok to make changes if you get stuck. Composition should be a fluid process, there’s nothing wrong with changing your mind.