Care to elaborate on this a little bit? I'm all for appreciating the arts, but in my experience no one has given me sagely advice along the lines of "Study great works of art, you'll learn to better perceive the flow of battles."
Thrawn studied a culture through the art it produced and gained insight into the psychological landscape of different species through their artistic expression. This allowed him to make deductions about what his opponent would do based on that insight. Zahn used this trait to add to Thrawn's mystique and explain some of the brilliant moves he made in outsmarting various New Republic commanders. YMMV on how plausible you think that is.
This sounds like Thrawn had a weakness for over-thinking his plans. Complex plans are generally bad ones, especially on the battlefield. Envisioning the path to Galactic dominance and actually achieving it are worlds apart.
Nonetheless, interesting character. It's great to see some military commanders being shown as competent, and it's also refreshing to see some good military action.
I wouldn't describe what Thrawn did as creating overly complex plans; it was more a case of orchestrating a series of events wherein everyone behaved in patterns he had already predicted and therefore had prepared a response for; and in cases where he did not have a response he was able to adapt on the fly and generally overcome others deviations from his expectations. His character was based on Irwin Rommel and Sherlock Holmes so between the two of them he has pretty strong reasons for being portrayed as smart enough to appear omniscient. Until his Noghri bodyguard stabbed him in the back. But as he said "It was so artfully done."