Kept a serious feel, media/professional/tech font yet added a simple icon referring to the clover part of things, yet is the same "O" used in the word clover
#2 i like this one. nice abstract clover with the squares. i don't like the colours very much, though (too colourful maybe). the font is a bit too "technical", i think
#20 - font is a bit too classic, this time. :) i think, a no-serif font (or one with less strong ones) might match nicer. and could you try how it would look if you put graphic element and text in one line?