Go to google , then images , then search after palm tree . Take a look at the big leaves . You should notice some things , there is manny , MANNY more leaves ! They are more "free" , they don't just point down or up or so , the point in every direction possible . And they also look diffrent . Still , you are a noob (no offense) . I an noob as well . :) 

I hope you use what I told you to manny other pictures . As long as it is not fantasy and you made the hole designe your self , always take a look at a picture and see what they actualy look like . 

(Sry for my bad english .)

Thanks, all noted. :)

Colours are okay. To not suck google some palmtrees and draw a couple on the paper just with any pen or pencil - you'll notice the difference with your picture instantly and next one will be at least good.

Or you can see how palmtrees are drawn in videogames and steal some ideas, but it will be second-hand experience.