Kids Art Hub:
Art for Kids Hub - YouTube
Okay, this isn't a game based learning platform, but it is a great art channel that students have really enjoyed of art. It is a great way to find a picture for the students to draw to accompany whatever they are learning. For example, if you are learning about dolphins in science and writing about dolphins in E.L.A., you can find a dolphin picture for students to draw to help them become more engaged in the topic. The only problem with this website is that you will have kids arguing over which pictures they want to draw if you give them the choice to vote for what they want to draw.
Silk – Interactive Generative Art (weavesilk.com)
This is something I use on a rainy day when students can't go to recess. Students seem to enjoy it. However, I believe it has been recently blocked by my district.