Being hidden is great and everything, but how do you know when it's getting empty?
I was going to hide mine until I realised I'd benefits from seeing the water level
I boarded around the whole tank and then cut a section off the side (almost like a level indicator on a kettle) same principle anyway.
Plus when boarded up you can utilise the tank surface, I've got bottle hangers, jetwash gun hanger, a shelf on top for floor mats and paper roll etc.
I'd reccomend getting a handy filling connector made and put on top of the tank to save taking the lid of all the time. This way you just plus the hose into it and walk away