Feedback from Evan Wallace:

It’s too bad that you can’t control texture parameters. Wrap modes don’t make much sense with textures from DOM elements but would allow for tiled background textures. While wrapping can be implemented manually via texture2D(u_texture, fract(v_texCoord)), it would be nice to have. It would also be nice to have control over texture filtering, or at least be able to give hints to the browser (mipmapping/anisotropy). There may be some scenarios where you would want nearest neighbor magnification sampling instead of linear, for example. Nearest neighbor filtering could also be implemented manually using texture2D(u_texture, floor(v_texCoord * u_textureSize) / u_textureSize) so it’s not a limitation, just an inconvenience.