The artwork of "Barrel Dragon" is one of the more extreme edits that isn't just a complete redrawing. His three revolvers have been edited to look more like laser guns, effectively equipping him with a "laser discharge system". Special effects have been added to emphasize this point, resulting in the edit looking much brighter than the original.
Barrel Dragon's effect and appearance, in the original Japanese artwork, are meant to reference the game Russian roulette. In the Yu-Gi-Oh! manga, Joey Wheeler explicitly makes the connection (fittingly, the one that played the card, Bandit Keith, claims to have played "real" Russian roulette at least once, during his slump after losing to Maximillion Pegasus).
This card's OCG/TCG artwork is taken from Yu-Gi-Oh! Duelist Duel 63: "Betting to Win!", specifically from the panel showing this monster with its decreased ATK and DEF, after being affected by the effect of "Time Wizard".