Not sure what you mean by "retaining wall".........would help if you posted some pictures.

Thin slats wrapped around the column.

If you are removing a structural wall you will need to have a structural engineer or an architect help you with the design. If the weight from above is going to be diverted from an entire wall to one column, the design must provide that whatever is underneath that column is adequate to support that load.

You could also hire a general contractor who works with an engineer or architect.

Once the column is in place a talented finish carpenter will be able to add the wood detailing that you want. You can provide them with photos of what you envision. A general contractor will have a finish carpenter on his team.

Definitely hire a structural engineer before you remove a load bearing wall to ensure new beam and post are appropriately sized.