We'd really like to be able to use our own CSS to style the page. The ability to add a logo and customize two colors is not sufficient. We need to be able to fine tune every bit of the styling, from the colors of the upvote number boxes, to the border radius, the font choice, everything. The feature upvote page is currently a total mismatch with our site, and it's terrible for a cohesive brand experience.
You could add in dedicated settings fields to allow users to adjust these parts of the page, but an easier solution, and a solution that allows more control is to allow the use of an external stylesheet.
Helpscout is a good example of this feature done right, and their execution allows near total control over the front end experience. They have you host the stylesheet in Dropbox to style the knowledge base pages. Link below for reference: