Velites and some Libyan skirmishers..

Carthage will have elephants early on VH campaign! Duh! Makes it harder? Yes. On Medium, they don't build the beasts until later on.
Well, OK then. Believe it or not, imparting information such as this is entirely the point of having a Scipii strategy guide!

When I first landed near Carthage I encountered a full-stack Carthaginian army with no less than 3 units of elephants. Arrow shooting elephants to boot. You need to be prepared to beat them. If you plan on doing it with Velites, they better eat their wheaties.