[OFFMason]

Okay, I am a law school student, and I must, as a matter of ethics, disclaim anything I say... so be forewarned that I offer no warranty or guarantee that my post is legally accurate in any circumstance.

This seems like a mixed question of agency and contractual aesthetics -- this may very well be a case of first impression.

As you are speaking about solicitors, I presume you are either in Britain or another English province or territory, so this ESPECIALLY is unlikely to help you.

It really comes down to the case law in your jurisdiction. This is likely a matter of common law (judge made law) as legislatures are too busy to make such minor league law.

The key question here is aesthetics. If the contract did not specify anything about the aesthetic direction/review process or if the aesthetic requirements are un-ascertainable or unreasonable the court will likely look to the industrial standard. Different courts look to this question in a variety of ways.