I think you're having problems with this: https://github.com/datastax/python-driver/pull/39. I'm sure that cqlengine isn't updated yet to take advantage of that fix (I just merged the pull request today), but that at least explains what the problem is.
As a workaround, you might be able to do something like:
from binascii import hexlify
hex_image = '0x' + hexlify(myImage)
myTable.create(..., image=hex_image)