To say that Tim Thomas' suit was too big for him, would be like saying that Topanga Lawrence was too hot for Corey Matthews. It's true, but it doesn't begin to get at the bigger (heh) issues at play here. It's hard to tell from this photo, but the shirt he's wearing is metallic gray and short sleeved. This may be one explanation for the pained look on his face. That very well could be the look of someone realizing that they look like an ass on national TV. It also might be the look of someone realizing they're headed to New Jersey.
Possible Explanation: Tim Thomas went to the tailor to get measured for this suit, but the tailor lost the measurements. So he had to eyeball it based on what he remembered of Thomas. When you're a regular sized guy like our tailor friend, the difference between 6'10'' (which Thomas is) and 7'2" (which this suit looks made for), doesn't seem all that large.