What do you mean by too young? Cartoony? Most figures do look a bit like cartoons, but if you make the proportions realistic the figure will be more realistic. I found a lot of tiger pictures when I did my tiger figure(in photos). In the end I did end up with a bit of a cartoon, but I went for realistic markings which helped his look.
Just play with your fondant/gumpaste mix until you get the shape you want and don't over think it.