Someone should probably do up a master list of assets to request for the stadium creator.
A couple of things I'd like to see are cricket nets and a manual style scoreboard in a couple of different styles. eg. Adelaide Oval to the basic board that might only show score and overs.
Trying to compile thoughts I've had over the past month working on stadiums:
1) Medium stand roofs for Large and vice versa
2) Tensile roofs like the ones in Ageas Bowl, Chennai, Pune, Sharjah etc
3) Media centers
4) Press boxes and grass banks as tier variations
5) Manual scoreboard
6) Training nets
7) Raised lower tiers, like Auckland, Dubai etc.
8) 3+ tiers for medium stands
9) Ability to set roof colors for all roofs
10) Extra-large sight screens like some of the South African venues
11) Different colors for seats in upper and lower tiers
12) Benches/steps instead of seats in tier variations
13) Buildings/Apartment blocks as props, a lot of English grounds seem to have them
14) Water bodies as backdrop
15) Ability to plop objects like scoreboards and pavilions on top of conventional stands
Some of these may already be on the way, and there may not be time/resources to get everything done. But having a wishlist is useful, especially for future game releases as well.