I really enjoy making half-atars. Since they use the upper half of your avatar for a compatible "you", and standard #Second Life and #OpenSimulator bones, you can use standard (or crazy) animations with them. So I hereby present my take on the next free Halloween avatar from Phaze Demesnes!
I've been experimenting with "ridable" NPC characters in OpenSim. I'll have this uploaded soon. We can then ride on a tiger.
You will be able to customize the avatar a little. You can change your hair. You can use a photo editing software to change clothes. It's not really hard but then it's also not very simple. You rez the tiger/avatar and drag and drop new textures on it.
For more information, read http://metaverse.mitsi.com/secondlife/posts/TigerRider/