The best alternatives to Mischief are Pattern, Everyone Draw, and Microsoft Whiteboard. If these 3 options don't work for you, we've listed a few more alternatives below.
What do you think of Mischief?
AssemblyAI— Speech-to-Text API with superhuman accuracy
Give your ideas room to grow with Microsoft Whiteboard. Transform your work into professional-looking charts and shapes on an infinite canvas with an interface designed for pen, touch, and keyboard. Bring your team together on the same virtual canvas, around the world and across devices.
VPaint is an open source vector graphics editor where the shapes you draw can have shared boundaries and be intuitively sculpted. It's a prototype you can download now, but we're running a Kickstarter to turn it into a more complete product: VGC Illustration.