Lacking the intimacy and subtle charm of the nearby (and often preferred) Columbia Harbor House, Pecos Bills serves a much needed purpose...capacity. This place is designed for efficiency, usually at the cost of extensive theming. Thats not to say the Pecos is totally devoid of charm, far from it actually.
The main entrance and ordering area is on the sparse side of theming, relying heavily on the "shit on shelves" mentality of imagineering found throughout Disney parks. (and, basically anyplace considered well themed.) But the dark wooden beams, muted colors, and southwest inspired tile work all ties into the theme well, and set the tone for the restaurant.
Found throughout the restaurant are black and white "portraits" of characters from the namesake Disney short featured in 1948's package film Melody Time. Pecos Bill, Widowmaker, and Slue Foot Sue are all featured in these adorable portraits...even though they do seem a little out of place. Maybe have the same shots recreated by actual people and aged? Otherwise they're pretty adorable.