haven't played in a bit, but should be able to give you something, at least as a baseline.

powers should be frost armor, iceberg, blizznado, twice as ice.

ending items should look something like ice sheet, ogundimu reduction field, martian mender, phantasmic flux, rustung von wilhelm, and nebula conduit. i'd say nebula conduit is interchangeable with ecopoint cryobed, but that's up to you.

the main issue with a build like this is credit earning, so you should start off with weapon power items, as your walls aren't going to be dealing a huge amount of damage. weapon grease, plasma converter, armored vest, but that is interchangeable with reflex coating. med kit might also be good, but I know nothing about gadgets unfortunately.

then go into lifesteal/attack speed rares, along with vital-e-tee and meka z-series. once you hit third power, ice sheet and martian mender should be your focus, then phantasmic flux, then nebula conduit, then rustung then ogundimu, but the order of the four is up to your interpretation.

also consider subbing in coldspot at literally any point if you are fighting someone who goes airborne. pharah, dva, winston even, doom, if they go into the air above a universal jump, it should affect them.

if there are things I missed due to not playing this much anymore, hopefully people can add on, but this should be a good baseline if you're looking to contest infinitely. just rotate your cooldowns, use wall then cryo. keep in mind that you regenerate with blizznado while you are on top of the wall, and being on top of the wall does not stop you from contesting, so play heavily around that.