The d8 and d10 are being updated to outlines of the full dice in the next version (d8 to a diamond shape, d10 to a flattened hexagon). As for the d20, the perspective might be a little forced/up-close, but there are already a few other hexagonal shapes in the font and adding another with vertical sides feels like it could cause confusion. I'll consider it for a future version, though.
Edit: although, with the numerals getting smaller in the next update I can afford to narrow the barrel dice, which would prevent confusion with a more regular hexagonal d20.