This are ready coloured symbols. I used Photoshop shapes, blend modes, layer styles and masks. So all symbols can be resized, edited and recoloured with no problem.

I started with creating mood board on Pinterest with different images related to Tiki theme.

Then I start sketching some typical and original objects on paper. It was Tiki bar buildings, Tiki coctail glass and other cool staff.

When I have several interesting symbols I move to sketching overall screen design in b/w. I prefer to sketch screens in Photoshop because of ability to implement changes very quickly.
So I finished with grayscale main screen sketch with all main GUI elements and symbols.

Move to colouring part. I prefer to start with neutral lighting for background. This way I am able to model any lighting and mood with filter layers in future.
So I created neutral background with sunlight and then changed it to moonlight. Correct symbols lighting also. 

Time to create some clear buttons. I did all buttons from Photoshop shapes + layer styles + blending. Everything can be resized and can be edited.