C is really good but I think the letters can be simplified. Maybe the N can just be an upside-down U and not connect at the bottom to the B. The B could also be one column narrower.
A. I liked C at first, but the N started to look weird and the ostrich looks like a duck. The block idea is cool, though.
The ostrich on A isn't super obvious other than the legs. Those are great. The neck and head need to be more ostrichy.
B is very pleasing in terms of colors and general aestethics but the nostrich (bird) element in B is almost unrecognisable and even confusing . A has the best bird representation out of all imo but A looks like it's missing something. C - the most original, creative and finished one, also lego connotations, vintage aestethics but for me this is not an obvious choice :) maybe bc the nostrich element sticks out of the general bounderies of the logo (cube)? There is sth unconventional in this but once you see C you will never forget or confuse it with another one, for sure.