Can we perhaps get rid of the shadows in the Victoria (and other) modes? They're quite irritating (to me at least), and a design relict of the 90s best left forgotten. Also, the extremely "round corners" of e.g. the "Reply to Thread" button could be made a bit less round.
Those are my personal preferences. Additionally, I find it hard to read the Victoria and the CK styles. DeepOcean still has the most balanced colour scheme: it's important that nothing grabs attention too hard, as it'll be hard to read then.