Please see this strip of color trial.
Is the man riding on back of a dog?

http://www.5iyu.com/ewshop/167/672/6702031.jpg

Dear Jin,

there is a problem with the image. Clicking the url, it appears: http://www.5iyu.com/zkeys_load.gif

Se copi ed incolli il link funziona.

Ok, thank you, now I see the colour proof essay.

Well.. I don't think that it's a dog, I think it's a very little elephant, a "child" elephant.
Look at this image:

it seems very similar, isn't it?
Well.. the auction description says:
Baule with Elephant; Colonial era; approx. 70-80 years, Cote D'ivoire
(from: http://www.binabashop.com/auction/2.htm)

Cheers, Marco.

Hello Jin and Marco,

it seems to me more an horse than an elephant.

Look at this object, sold on line at http://www.ioffer.com


I think man-on-horse or men-on-elephant is a frequent iconographical element of the Baulé people from Ivory Coast. Definitive solution of the enigme could be found here:
http://www.amazon.fr/divoire-tr%C3%A9sors-mus%C3%A9e-dabidjan-vevey/dp/B0000DNZTI/ref=sr_1_4/278-5397860-1904505?ie=UTF8&s=books&qid=1278065150&sr=1-4, or in the Abidjan museum

Thank you all.
The carving arts of Irory Coast seem much interesting.