Re exporting Buddha images- have found this info for you.
Not sure about exporting large pieces of furniture but I would imagine it would be straightforward. I have seem many tourists looking at furniture! I will see what more I can find.

Shipping furniture out should be easy enough- any reputable shop will sort it out for you. I found quite a handy guide to Bangkok shoppping when I was looking for info for you. Have a look here.
In the meantime, perhaps you may still get a reply from someone who has actually bought furniture!

We looked into it briefly when we were in Chiang-Mai about twelve years ago. It seemed fairly straightforward and most of the furniture shops are geared up to do it, however at the time the furniture being produced was not what we wanted, what was being produced would look very dated now. However the furniture being produced now looks great.It seemed just a case of using a trustworthy company to ship the furniture to your door...you just booked space on a container ship which was not hugely expensive. I assumed that Customs and Excise in the UK would take a cut some where in the process.

Another concern was that some wooden furniture does not fare very well in our central heating. I know my Dad had some hand made furniture shipped back from Singapore in the late sixties and some split in our centrally heated environment.