its a bit big imo
most sigs are like 350 x 150 but i dont really care what size you use
i dont really like the idea of having those 'c4d' or abstract renders or whatever on sigs unless its a grunge sig cuz they would blend nicely
as for fonts you would wanna use just default fonts
and if you go for pixel fonts make the size small
i'll give you a 7/10
Coloring: Pretty good you should try making it multicolored on the 2nd one
Brushing: Normal
Render: Not like
Text: Its ok
Font: Try to use a default font
But then again i'm a n00b too, but thats what i learned while im still learning just keep that in mind