Just a guess but lots of games optimize things like textures and interface graphics by creating atlases.
Think of an atlas as a single large image file that contains many different images side by side. For instance all the different card backgrounds in one atlas. Here's an example of a texture atlas containing different ground tiles.
If you're loading up a game of magic, all of the card backgrounds might be contained in a single atlas, requiring only a single asset load instead of many individual asset loads. Now when the game requires a black background it references the xy coordinates of the atlas that contain only the black background.
If you're talking about a game containing hundreds of thousands of magic cards, you don't want every piece of card art to include pixel data for the card backgrounds. Instead you keep the backgrounds in one atlas and compose those with the card art and other elements like the text box and P/T elements to create the final card image.
And finally, since the software is referencing coordinates in an atlas for pixel data, something can go wrong. If the numbers for the coordinates get messed up you could reference the wrong background. If they get really messed up you might conceivable end up referencing a position that shows half of one background and half of another. Depending on resolution the pixel data for the background might also be stretched to fit the required area, this stretching might also go wrong, for instance when the background art stretches far more along the vertical than the horizontal axis, distorting it.
Anyway I have no idea how MTGO really works behind the scenes but these sorts of image constructions are common in games and software.
I have invited repeatedly Doctor Worm (the user that started this thread), to notify the authors of the content he thinks we misappropriated. The report button on steam is also fine.
I will restate here what have been stated multiple times:
The sounds are either public domain, made by ourselves, or donated by volunteers. The rest of the textures, voxel terrain, ai, and everything else we built from scratch. Not a single one of the authors of any asset we use has any issue with what we are doing. We paid them what they asked for and complied with their terms.
I wish doctor worm would indeed contact whomever he thought we wronged. Instead for some reason this seems to be a personal thing for him.
We do not have potions and enchanting. In fact, we have repeatedly rejected them for the simple reason that they are present in Minecraft. Magic is spells you cast on mobs, and flying. Both use mana, which you can improve by leveling up
Leveling upgrades walking, swimming, flying, strength, walking, etc... It is the main point of the game.
We are actually replacing the textures: http://www.blockstory.net/node/2507 to make them higher quality.