Some of the art the developers have shown was revealed as stolen (or copied) too. This concept art dates back to the 1990s, further proof that they were ripping things off even then.
You can see from this image comparison that the concept art for Grunger is nothing more than a trace-over of a detail from Clyde Caldwell's cover painting for the Dungeons&Dragons game accessory "The Orcs of Thar". The orc on the D&D cover is the same as Grunger, right down to the head he's stepping on (which ultimately became Edd The Head in LotL). Grunger looks completely different ingame.
The concept art of the "Keep of Lost Souls" is also copied from Keith Parkinson's painting "Dragons of Desolation", originally commissioned for the cover of the Dragonlance role-playing game adventure of the same name, later the book "The Art of the Dragonlance Saga", and the computer role-playing game "Champions of Krynn". Comparison:
The Shadow Knights from LotL's Concept Art look like the villain dragon knight Haagen von Diakonov in the game "Dragon Lore". For example this one on the game's cover:
Cranny Faggot's Concept Art looks very similar to Meg Mucklebones in the film "Legend".
Alone in the Dark 3Edit
The concept art of Masa is copied from the cover of Alone in the Dark 3.
Sketches with unknown origin, help is desired.