The most interesting bet that I've seen is (if you want to gamble)
Bears +21.5 (Alt Spread) -750
There's no max bet on this either
and although you're risking 7.5:1, this is almost a guarentee
The complete list of alternate spreads is below
Colts +10.5 (Alt Spread) -900
Bears -10.5 (Alt Spread) +600
Colts +7.5 (Alt Spread) -750
Bears -7.5 (Alt Spread) +500
Colts +3.5 (Alt Spread) -450
Bears -3.5 (Alt Spread) +325
Colts -3.5 (Alt Spread) -170
Bears +3.5 (Alt Spread) +140
Colts -10.5 (Alt Spread) +160
Bears +10.5 (Alt Spread) -200
Colts -14.5 (Alt Spread) +240
Bears +14.5 (Alt Spread) -320
Colts -17.5 (Alt Spread) +300
Bears +17.5 (Alt Spread) -400
Colts -21.5 (Alt Spread) +500
Bears +21.5 (Alt Spread) -750