We had 216 16 17 Falken Allroad Van tyres on standard 17in rims for our Iceland trip. I got these as they had a good chunky tread but also had the snowflake on so suitable for snow and can fit chains on that size as well. They performed really well on the f roads in Iceland, gripped well on gravel and rocks and surprisingly quiet on tarmac. I know of someone who fitted big wheels with grabber type tyres for an Iceland trip and found that the tyres were hitting the wheel arches. I guess it depends what you are doing with the van. If you just want the look then fine but for any kind of offroading personally I would always go for 17in which also means the spare will fit easily under the van. Re arches I think they look great but from past experience arches just gather crap behind them and lead to rusting. Certainly in Iceland the amount of dust and gravel that accumulated on the van was unreal so arches would certainly have been full of it.