Do you have DIY ideas for whiteboards?

Perhaps I am misinterpretating your question, but I thought you were asking how to make one.

Cheapy white formica type boards from hardware/big box stores work well as long as you take care of them. So does glass. Do you have old windows, mirrors or picture frames? They are a great alternative, especially if you can pick them up cheaply. Put them in front of a light coloured wall or back them with paper. Apparently there is a kind of dry erase Contact paper. I haven't used it.

Avoid using dry erase brushes/erasers...old terry cloth works better. Rubbing alcohol, is good for cleaning. Blue dry erase markers often make a bigger mess.

I just saw this:

http://rumkin.com/reference/whiteboard/surfaces.php

try painting old cookie sheets from the thrift store wit dry erase paint. Michaels has it.. Not cheap, but using a 50% coupon it was only $15.00 makes about a quart.

I painted a door with white board paint. But you could go to your local junk shop, buy the biggest, gaudiest, ugliest and cheapest piece of art and use the paint to cover the image and voila!