I have the idea to commission a local artist to make an artistic version of a couple of figures I often use for presentations, and that I would probably use for my thesis cover. The figures does not present any numbers, but rather conveys the general idea behind the work (subject area is theoretical chemistry). The artist does not have an online portfolio, but a lot of his work is probably best described as "kind of abstract, bad for people who suffers from trypophobia".
I already know that most of the conservative seniors at my department would think it is a bad idea. Normally we go with quite bland figures and monochrome covers (there is nothing in regulations stating that we can't spice it up though). But I am interested in hearing what you would think, if you saw such a thing, a bit out of the ordinary.
I would, by the way, probably pay him out of my own pocket, as I don't think my grant includes art money. And I am perfectly fine with that.
It's your thesis, and so long as the work --- including the cover ---conforms to the requirements set down by your institution, then I see no problem with it. Yes, you might upset some of the more conservative of your colleagues, but if you continue in research no doubt you will in future perturb the status quo again.
The only concern I have is whether such an unconventional decoration would influence a grader. However, I suspect you are considering the final version of the thesis, after any corrections set down by your examiners, so this isn't an issue.
Naturally, you should give credit to your artist.