For now the textures should use the typical sizes for 3D textures, those will work correctly. I will look into the issue, this is not intended.
There may be some resulting blurriness for static sprite images though when using weird sizes, because the editor builds a combined image of all used textures in the effect, so in that case it's best to stick to 128 or 256 to ensure maximum sharpness.
You also want some padding on each side in the tileset to ensure they don't bleed into each other, in the original they sat at the bottom of each tile.
Could be useful to add a toggle to turn bilinear off for effect textures, this would help with the bleeding if the tiles have no padding.
That should help with pixelated styles like this. I can prolly push that into this week's runtime patch, then later add it to the editor too.
Attached a version that loads correctly.