I went to two christenings last year and they were both at village halls after the church ceremony. They both just had a few flowers and some balloons. I don’t think you need to go overboard!
We are holding it at a servicemens club & hiring one end of a room lol. All the decorations we are doin is couple of balloons & some banners by the food x
I think it can be whatever you want it to be! Id say most christenings I've been too have been in people's home and from what I remember there hasn't been decorations. I've need to one of a lovely hotel around Christmas time so it was decorated festively. I've also been to one where they hired a venue and had decorations. At ours I've hired the village hall and do plan to do minimal decorations but its mostly that's something I really really enjoy. I think there is zero expectations to have decorations