Pick a theme and run with it. Tie it to a path, a neighbourhood, involve, service groups, seniors, youth and everyone in between. Sure you can set out guidelines, nothing offensive, must fit the theme, maybe even limit the colours that can be used, all these things can be sorted. It may even be that people have to submit their ideas first before allowed to run with them. Of course check to see if there are restraints with the owners of such pole, not covering identification tags, or having things on them that impede them from going up or down them as necessary.
I painted a telephone pole outside my house, I learned that there are huge vertical cracks in them making it difficult to do some fine details. Solution, wrap them in canvas then the sky is the limit, and then they could be worked on inside and attached later much easier.
With some thought even telephone poles could be a real art piece, and an expressive outlet for our community. We have a lot of talent in our community, and encouraging and fostering creativity is one of the best things we can support. Creativity is a needed and sought after 21st century skill. With the world changing as quickly as it is, we need creative thinkers.