That rather depends which Viburnum - V. davidii for instance never gets more than 4 or 5 feet high.

Viburnum opulus does get to be a big shrub. I suppose you could grow it on a 'leg' so that it would make a small tree.
V. cylindricum is a small tree in its own right, never seen one though.
V lantana is the Wayfaring Tree, but more often a shrub than a tree.
V. lentago may be a tree, again never seen it.
V. prunifolium is a small tree, never seen it.
So, I suppose any of the more robust tall growing shrubs could be mae to look like a tree by only allowing one stem to develop as with standard Roses or Fuchsias. Interesting to try.