Twitter for me is the best social media to promote on. However, it can completely depend on which type of company you are, the product you sell, and your target audience.
In my opinion, Facebook and LinkedIn are the two absolute necessity's for YOURSELF and YOUR business if you want to create social media awareness.
Twitter is most commonly used these days, however, I would say 70-75% of users are between 17-35. Not that you wont receive customers that fall into this age bracket, however I wouldn't focus, at least not the majority, of your attention for advertisement in the direction of twitter. Furthermore, although there has become a rapid increase in the use of imagery and video content on Twitter in the last couple of years, moving away from simply written digital 'tweeting' content, there is still impetus on the written content voiced in tweets, but you get a limited amount of characters.
If you were to add a detailed and fairly sophisticated description of your artwork and boardgames, twitter won't give you much to work on.
Facebook and LinkedIn, provide the ability to use images of mostly all sizes, almost unlimited character storage for you to add depth into your posts, and from the experiences I've had with these two social media's, there seems to be an older demographic for you to expose your products to. In my opinion, the target audience of around 35+ will be more suited to your product, and more of these are found on Facebook & LinkedIn - however, you will know more it's your business!
Just one last point, I would definitely consider LinkedIn for your business. There is a lot of businessmen/women, who post for engagement and advertisement of their achievements and their businesses. You will attract (tongue in cheek) quite a lot of people who may have a nice budget to work with to spend a few quid on the type of things you are selling! Furthermore, it's a fantastic place to find partners, investors, and lots of people who are willing to give you great advice. Connect with as many people as you can! Dom