From my experience and friends/acquintances I have an impression that in arts they usually adhere quite strictly to the standards and set a required number of letters and/or pages for the thesis. In the exact sciences the situation is the opposite. The examiners either ignore the looks or value aesthetics instead of standards. And your thesis would really be valued.
There are three persons that could give you a precise answer on this, please consult them if possible:
- Dean. This is the person overlooking everything in the faculty and setting the tone. This person has probably decided if adhering to the standards or
- Director of programme... or something like that. For every study programme there is a person that organizes everything - plans courses, finds the examiners etc. This is a person that actually tells the examiners "please check thoroughly if they adhere to this standard". Or maybe the director ignores the standards and only tells examiners "please focus on the content unless the formatting is blatantly ugly".
- Faculty secretary or whoever you hand the thesis to. This person will know in which cases the theses are handed back to students. However, they tend to exaggerate. Either because the students twist the truth ("rejected for formatting? oh boy, you really have to have everything inch by inch as written here..." when actually the font changes both the size and typeface from section to section) or they simply want to put you as far as possible from the rejectably bad formatting.
When I had to write my first thesis, the dean made a gathering and told everyone something like "please understand that the university standard is written so they could reject terribly formatted theses, take those guidelines with a grain of salt". He told us that the default LaTeX style will be better than the guidelines and we can surely ignore the Times New Roman requirement.
At the end of the day, it's unlikely that the thesis will be rejected for technical reasons. If it is, the secretary will usually be the one to reject it on the spot by saying "please re-print these pages, I can't accept it". If it goes to the examiners, an enjoyable look will most likely ... be enjoyed.
Don't know how it happens at your place, but I had a comission to whom I had to tell the contents of the thesis. Then one examiner who had to read the entire thesis, told his evaluation on the written work. The comission then decided their thing while handing each other the thesis for brief looks. I think that good pictures would be the only thing they could notice and evaluate at that point. At either point it is unlikely the decision would be skewed either ways because of pictures. Would you yourself think worse of someone for that? But you wouldn't rate a bad work higher either if it had nice pictures.
Unlike most others I suggest - surely do it! You will have a copy of your thesis for the rest of your life to enjoy. If you can get it through with the pictures, go for it! I really didn't understand my mates saving few bucks for cheaper cover, thinner paper and grayscale printing. If you like your thesis beautiful, you will not regret making it beautiful when you look back 10 years later.
P.S. I hope the picture is grayscale because of the original. Because I surely suggest you to use colour and to print the thesis in colour.