I mean, it is possible to google something around > Medieval game ui (user interface if un-aware) > game ui kit > game ui boders...
With some of the "sprites" within the picture, those are just dumped from the RS Cache, I can upload I think the 830 or 803 sprite (image) dump I have on my PC if you'd like to go through the folder and look at some nice sprites that can be used as elements for a paint.
From the looks of the example paint you've posted, the main background (blue middle) is just a background-ish RS sprite, as well as the coins and xp 'buttons'. But like I stated above, your best also besides googling for game ui kits, is possibly something like > how to create a cool game ui in photoshop > etc etc.
I haven't really ever searched any of the suggestions, but to me, that'd be your best bet.