I think the main aim is to avoid getting drawn in to the wedding frenzy which can easily take over, utilise the talents of close friends/family and go for something a little different which they really like to make it a comfortable and memorable day.
In our cases DD1 had 28 guests - their close friends and really close family - we took over a country house hotel for the weekend and the dogs came too. Monsoon dress, big hat, novelty cake, BiL took photos, SiL did flowers, mini bus to registry office. Wonderful weekend.
DD2 waited until her DB was working in Antarctica, we were on holiday in NZ and then 'eloped'. Married in local registry office, with sister and friend for witness, then rang a few friends who rang a few friends and they all meet up in their favourite bistro - 40 turned up - the guests paid for their own and the happy couples meals and booze. We had a posh family meal with DSiLs immediate family on our return and gave them money towards their new home. Wonderful evening.
DS married in a country house hotel on the Broads with 24 family and friends followed by a reception on a river boat which, with 50 more guests, collected them from the hotel and pootled around the Broads for 3 hours. The boat worked out surprisingly reasonable and no wedding cars. Aunt made cake and again BiL did photos and SiL the flowers. Wonderful weekend.