There are many things that will influence as to whether I will do your requests. The following is not an exhaustive list of what influences me to do or not do your request/making art:
Positives: Detailed requests, factbooks w/ context, banter
Neutral: Asking for just a countryball, background-less requests
Negatives: Emblems, long requests, requests with too many flags (decided on a case by case basis)