Hi @essential1234, sorry for the delay. There will be a new "Magento Marketplace" launching shortly where you can purchase and download themes for Magento 2. It is not live quite yet.
You can also develop your own themes, but it is a developer based experience at present. There are different levels of theme work you can do. You can adjust at the CSS level, the HTML level, the positioning of "blocks" on the screen via "layout instructions", but if you need more significant changes you can develop a module that changes the behavior of the product. Magento has extreme functionality in this area.
There is online documentation if you want to read up on it at http://devdocs.magento.com/. Have a look at the "frontend developer guide" in particular. This guide is designed for developers however (not sure your background).
There are also a few books starting to emerge on Magento 2, which probably touch theming. My best suggestion there is just to try a google search - there seem to be more every time I look these days. (I am also working on a book to introduce the basics of theme design, but that could still be a month or two off from release - and again is geared for developers.)
Magento however is a pretty sophisticated system. It has a lot of power and room for growth, but complexity comes along with that. Something for you to consider when considering options. (I believe in picking best tool for the problem, not just "Magento every time". Just don't tell my boss I said that! ;-) )
