ARC Guidelines for new structures

We are a new upscale town home community and are just starting to get some requests other than the easy ones of fences, doors, patios etc. Right now it is a request to build a pergola. What are some of the reasonable guidelines that have been used with regard to materials or looks, size etc. One thought was for the committee to research some acceptable plans/pictures and off a choice of say 3-5 styles with guidelines as to acceptable materials used and colors etc. The ARC inexperience "botched" one such request with not so pretty results (the drawings and the end results were very different) and we want to make sure that doesn't happen again by offering some guidelines as to what is and isn't acceptable. Am looking for some wording,ideas etc we can use.
Thanks!