#1: It's all about the background! Here we see the subject in silouette so it becomes about form as well. I like the head being in the large circle of confusion at the top. I like the geometry of the tail forming a circle to match the COC's of the background (fortunately it doesn't wrap around one which would be hookey .) The angle between the twig and lizzard makes a neat "Y" shape that I like as well. Great composition. Maybe go totally silouette - presevering some to the twig and lizzard might not be necessary - plus dropping down a stop or two might increase the drama of the background.
#2 #5: I've never appreciated the idea of photographing something that is camouflaged.
#3: The eye not being symmetrically place in the socket disturbs me.
#4: Best one. Love the background - really enhances and brings out the lizzard. Love the contrast between tree and background. The tree compliments the lizzard's patterns. Like the lighting. Great shot.
#6: Doesn't work for me. Not sure about the lizzard "walking off stage". Don't like the color scheme. Not enough contrast beween background and subject. Found the brown spot below the yellow patch at the top to be the most interesting thing here. Don't like the "straight down" view. Image is too flat geometrically. Don't like the flat lighting - lizzard needs some shadowing. Don't like to be negative, but these are my opinions (which aren't worth much ).