I like the design.
I think it asks for a heavy saturation.
This card should look better with stronger colours as it represents something, a power. It needs to stand out from your regular game UI.
By keeping the frame of each card (the edge ornaments) the same, you can afford the variation brought by the strong colours because you remain consistent with the style of the game. Additionally, the players will most likely appreciate seeing their favourite cards or heroes with strong colours.
For illustrating my point, here's a comparison. If you increase the saturation by 90% and add some slight red colour to the middle tones:
As quick reference for theory and inspiration, I like to keep at hand this article from Valve on character art: http://media.steampowered.com/apps/dota2/workshop/Dota2CharacterArtGuide.pdf