Update (March 1): I found this photo on Wikipedia. The photo was taken by a US Defense Department employee:
After thinking about Arba3een the last few days, I couldn't help but conclude that it is somewhat ironic that Iraqis are now allowed to make the pilgrimage to Karbala thanks to the USA. I just read this article, which Maury linked to in a comment: '"Under Saddam, those who went to Karbala were killed or had their legs shot so they could not walk again," said Hussein Hamad, 74, one of the pilgrims in the giant procession snaking towards the city.'
Also Abbas Hawazin has just published a good post about Arba3een and the Shia. If you want to see what a Shia shrine looks like, inside and out, watch this video, which I shamelessly stole from Abbas's post. Thanks Abbas!
PS (March 2): I should have said "it is somewhat ironic that Shia are now allowed to make the pilgrimage to Karbala thanks to the USA."