Well...the casual gamer, first of all, would likely have enough content with the unmodded Dominions to last a lifetime. I personally recommend *not* going casual. This isn't really the game for that. There's too much to learn, and do, and-for me anyway-too much joy in the learning and doing-to take the game lightly.
That aside, I'd recommend the CBM mod-it's shaping up very nicely-as well as any of the terrific Warhammer mods that have come out. They look nice and are pretty straight-forward to understand and use, and they're based on a fantasy wargame that has been aged like fine wine for decades.
They'll give you an idea of the quality of mods out there, and what can be done graphically and thematically, and maybe inspire you to get a little deeper down the rabbit-hole.
