Portraits: if there is more support for changing to squares, I’m fine with experimenting with it. Sizes are unlikely to change, but each can be expanded by clicking the portrait or character name.
Corp/alliance: see answer here
Preview part of op: I’ve heard a few others mention the same. Something we can look into if it can be done.
Signatures: We have opted for biographies instead of signatures. Biographies are readily available with a single click. If there’s an argument to be made - other than saving a click - to having signatures, and it receives sufficient support, we’ll be willing to reconsider offering signatures.