In class we had some sentences with intentional mistakes to fix. One of them was "きれいそうなsomething". The mistake was that you don't say that because if you're looking at something, you can tell if it's きれい, so you wouldn't say it "seems" きれい. Is it really something people would never say?
When you are directly seeing some beautiful thing in front of you, you cannot say something like きれいそうな絵ですね. Saying ～そう always involves a speaker's guess/speculation, so if you already know that it's beautiful or not, you cannot use this expression.
An analogous case is おいしそう ("Looks yummy"). You can say this before eating something, but saying おいしそう after actually eating it will sound very strange. (Because it no longer appears to be yummy but in fact is yummy or not).
For this very reason, as @Chocolate mentioned, in situations where you are not directly seeing something, saying きれいそう is perfectly fine. When you have heard how beautiful something is, you can safely say きれいそうですね ("Sounds beautiful.")
A Japanese language teacher said 様態のそう(な) can't be used in the case of 見たらわかること(You can understand when you see them). For example, あそこにきれいそうな人がいる and 彼女はきれいそうだ would be unnatural because you can understand whether she is beautiful or not when you are looking her.
However, as the comments, 夜景のきれいそうな町 and 部屋のきれいそうな芸能人 make sense. This きれいそうな is adjective for 夜景 and 部屋, not 町 and 芸能人. That is "City whose night view seem to beautiful" and "Entertainer whose room seem to be beautiful". This would be speaker's guess.
This is a source. http://nihongomemo.hatenablog.jp/entry/2015/03/27/104605