yeah, ren shan ren hai is a pretty good one, and it's also probably one of the more frequently used ones.

Mandarin Chinese:

I thought of a couple involving animals.

沉鱼落雁 (chén yú luò yàn) - literally "sinking fish and grounding geese" - describes a beautiful woman.

虎头蛇尾 (hǔ tóu shé wěi) - literally "having the head of a tiger and the tail of a snake" - meaning: 1. having a strong start and a weak finish. 2. describing someone who is treacherous and doesn't do what they say they will.

Lots of idioms in Chinese are "chengyu" consisting of four characters.

mm good idea, maybe there really aren't two dots on top of the 看.

the top right is probably 混水摸鱼 which is an idiom my dictionary translates as "to take advantage of a crisis for personal gain". the top left three characters might be someone's name. the bottom row: no idea about the first character. second character is probably 着. last two characters are probably 罚款 (fine, as in paying money as a penalty). the handwriting is pretty sloppy.