David,
Yep, you can usually lease the credit card terminals from your merchant services provider. It costs extra for the terminal, and with the new credit card rules, there is alot of extra stuff you have to deal with when you have, and utilize, a terminal with regards to liability.
The easy fix would be to just have a laptop and utilize the virtual terminal online or with a USB swiper, which is what I do.
However, if you really really must have a terminal:
Wireless Credit Card Terminals at Merchant Warehouse
As far as the walls go... I am not sure, but I was told they are sometimes provided in a generic fashion, but otherwise people have their own set-ups. I have a client who is an artist (painter) who sells out of the Waxlander Gallery in Santa Fe. I photograph his commissions when completed (his work is really cool, but sells in the range of 3k - 10k so far too steep for me). He has been trying to convince me to try out one of those art deals, so I was glad you checked out the photogs to see there set-ups.
If you have a moment, chat with Warren Harris, I know he goes to these things all the time so he has a wealth of knowledge.
Hope that helps.
Warren