Concept art is a notoriously demanding thing to get into. Some of your ideas have merit (particularly the colours used in the second image), however I think the execution here needs more work.
Concept art typically has much more of a ‘painterly’ feel to it. It is designed to evoke a mood and atmosphere, and bring the setting and themes of the game to life. For this reason, the highly stylised vector approach you’ve used here doesn’t really work for the fantasy theme of the game as you’ve described. This is especially apparent with the characters, which have more of a ‘South Park’ feel to them. While this style can work if used well, I personally don’t think it’s a good fit for the genre of your game.
Kotaku run some great showcases of various concept artists and their portfolios. If you’re looking to use these pieces as a way of building interest or investment, having a look there could help you refine them. Good luck!