It's not about imagery helping the team "perform better" it's about being proud of your identity, your club, your memories. Seeing them on display, especially in the place you go to watch your club try and do similar in a venue which has often been argued we feels like a 2nd or 3rd most important tenant that perform there. It's not just about attendance either. It doesn't feel soulless simply because of the attendance, we've had worse atmospheres with bigger turnouts so that's another debate.
We've got plenty to look back on and be fond of. Some wonderful players, some wonderful results that could be on display around a ground that is black, grey and plain and could easily be uplifted. You mention Coventry, even they have a wall of fame dedicated to those who've represented them in the past. A small gesture that goes a long way. We've got, what, a wall of season ticket holders which is nice and could be added to, surrounded by 15 year old pictures of school kids in MK who probably don't even know they've been on that wall for nearly 2 decades?
We've got plenty of good pictures of wonderful times gone by that'd add character and bounce to a stadium that looks like a shell of nothingness. Could be murals around the concourse, on the exterior of the ground etc that leaves no doubt who plays here.