Better, or rather more, lighting perhaps? I always find platform level gloomy because the areas above the tracks are unlit, while not necessary for passengers addressing that would IMHO improve the overall ambience.
Absolutely agree.
I also think they really could have prioritised fume extraction - while they have some fans in place they seem to generate more noise than providing fresh air. It would scupper the fancy shopping centre, but some ventilation shafts to the outside would help. The daylight wouldn't hurt either. But the priority was to build a shopping centre and hide away the trains, alas.
It only takes a couple of voyagers to fumigate the platforms - you can hear the fans starting to spin up but by the time they have done that I'm already choking from the smell.
Additionally they could have (maybe still could?) looked at imposing better crowd management systems. For example, stacks of people piling off trains while stacks more try and push on at the same time for a through train. Queuing systems up top to allow time for alighting passengers to make their way to the escalators before admitting boarding passengers would make the whole process more pleasant and civil.
Finally, not requiring people to have to scan out of the barriers then scan in again to change between some platforms on the A end would also help a huge deal. It's a really clunky experience having to know to go to the B end, or have to be let out and let in again as the barriers regularly reject my through tickets, necessitating me taking up the time of a member of staff.
It's not an *awful* station - but given the somewhat recent refurb there's a fair bit of valid criticism, especially for the issues introduced by the refurb.