Reskin apps for Android and iOS

General information for the business: I am starting a new endeavour in app development and looking for a quick way to get going... app reskinning seems a decent place to start, so I'm looking for someone experienced in app reskinning, who can do some reskinning for me and be available to give advice as I learn.
Kind of development: Customization of existing program
Description of requirements/functionality: I am looking for someone who I could possibly work with on a longer term basis. I'm looking for someone who can give me value for money (not necessarily who will do it for the cheapest price!) and dependability.

I currently have one iOS app ready to go, but it needs some work to be successful.

The app is "Subway Skater": a basic, 2D platform game. https://itunes.apple.com/us/app/super-subway-skater/id1060659393?ls=1&mt=8


I would need someone who can:

Design new backgrounds
Add new levels
Create a character choice (there is only one character at the moment - I am thinking along the lines of having a couple of basic characters and then some special characters available to purchase)
Further monetise the app
Use their professional judgement on how to best reskin apps.

I also have a number of source codes (some are android, some are iOS) that I would like someone to, basically, get creative on and show off their capabilities! :-)
Extra notes: Please give me an overview of what you can do and how much you charge for each activity. If you could also send some examples of previous work, that would be great. I have placed this ad at an hourly rate of £15, but please feel free to send any reasonable offer for consideration.

Thanks!