I don't know what size you're thinking of, but I think having a sink in the utility room is invaluable. We've used ours for soaking stained baby clothes, washing hands when we come in from the garden, washing anything that is very dirty (ie from the garden or the garage) etc. Splashback behind it is easy to clean.
A cupboard that is wide and tall enough for the ironing board, vacuum cleaner, carpet cleaner, house sweeping brush, dustpan and brush, mopp and bucket, iron etc.
Think what you need to get out of your kitchen or under stairs cupboard etc and work out your storage around that.
What about power points? Make sure you have enough. For example, the ironing is done in our utility room, so I need a socket that is quite low. Its also handy to plug the vacuum cleaner in the utility rooom whilst I hooever just outside, so a low power point is useful for that too.
If you're not having a tumble dryer, is the room wide enough for your clothes horse, or possibly two?
Have you looked on pinterest for storage and configuration ideas? I have a load of utility room pins on mine, and I barely use pinterest.