The folks over at Cornucopia3D are holding a Game of Thrones Fan Art Contest all this month, until June 30th. Create a landscape, city, hamlet, or castle from Westeros. Or you can illustrate an event from the George R.R. Martin book series or the TV show they made from it, such as a coronation, treaty negotiation, battle, or assassination. Of course, you can not use any copyright images from either source, you will have to create your own original artwork inspired by the series. There are a few other rules, which you can get from their web site, along with a list of the prizes. If you don’t feel like entering the contest but want to show off some of your artwork they have a ton of non-contest galleries you can upload to as well.
They also have some software and 3D modeling resources you might find useful, including a free copy of Vue 2014 Pioneer. If you haven’t used Vue before, it is one of the best 3D modeling programs available for easily creating terrains and landscapes, from a single scene to an entire mountain range or planet. The Pioneer version is a full product, not crippleware or a limited time trial, but it is their entry-level version. There are modules you can buy to upgrade it to some of the functionality of the other versions, such as 3D model importing with bone rigging and texture/bump mapping, but it is a great way to get started on creating your own worlds.