The test isn’t really the problem.
First you are presented with a series of dos and donts regarding the iStockphoto policy and quality standard. The test just makes sure you read and understood all these mini lessons.
The real problem nowadays seems to actually get accepted as contributor. You have to upload 3 representative images of your work. These will get reviewed by a jury and you get contacted if these are up to the standard iStockphoto expects.
As iStockphoto gets flooded with many new applications for some time now, they seem to have risen the hurdle to an extraordinary high level to get accepted.
Thats the message I got after trying
At this time we regret to inform you that we did not feel the overall composition of your photography or subject matter is at the minimum level of standard for iStockphoto. Please take some time to review training materials, resources and articles provided through iStockphoto. The photographs provided in your application should be your best work. Try and impress us, we want to see how you stand out from the crowd.
And these were the three images I submitted
Looking at some of the stock images already present or newly submitted ( and accepted) by already accepted contributors, I came to the conclusion that entry level images are measured quite differently.
After a rejected attempt you have to wait 72 hours before you are allowed to upload again.
I think I will try again nonetheless and see if I can get accepted eventually.