Chinese elm, Ulmus parvifolia. Also called "lacebark" elm.

Second the Chinese/lacebark. Only issue from making it more popular is abundance of low-hanging branches IMHO.

Very desirable tree. Like Dan says, it may benefit from trimming off some of the lower limbs, as mine has (but the one you show looks fine IMO). Trunk shown below this past spring:

was going to say crepe myrtle until I seen the leaves....