It's polite to make a suggestion, but in the end it's a decision made by "both" parties, it's really (often) a compromise, the more educated person should win out, and the client should listen to the educated.
I actually won't do work that I don't think looks good (after all) it's a reflection of me, my abilities and is a walking advertisement for me.
If a client wants enhancements, that simply don't "enhance" and makes them look ugly, I will send them elsewhere.
Some may call this "attitude", but I have built a reputation over many years and wish to maintain it.
If it doesn't look "beautify" I don't do it.
But thats me ......