Start with a realistic lion picture (to get a standard lion idea).
Nowadays most regular and famous type is the diamond/line made lions.
To get ideas for your own, maybe the best choose will a colored diamond styled (I have never seen before that type)
Upper arm lion tattoo
(source: http://tattoome.tumblr.com/post/112256737366/matt-adamson)
Bit more artistic upper arm lion
Made by www.tattootemple.hk
Chest Lion tattoo
Made by Elvin Tattoo
Full Chest diamond Lion Tattoo
Diamond styled made by Felipe Kross