Cut to the chase: is a MR needed for a silhouette of a person if it's totally black against white (i.e. photoshopped to make sure)?
This is a rough idea of what I mean http://www.lizworld.com/Sil.jpg. It's not finished - the edges are pretty jagged, and I haven't even checked that the black is all 100% black - but I'm not spending time on something that's a non-starter; I've probably got about 15-20 in the series.
No speculation please - only if you've had silhouettes without MRs accepted or rejected at iStock. Thanks.

Sorry, no previous experience either but looking at your image I would very strongly assume that IS wants a release for that.

Not only to protect the model but to verify that you took the original shoot.

After reading your post I checked my port on IS and found three of mine all rejected a couple of years ago with the following reason:
Rejection Reason

+ Please provide Information on the original source material indicating the source of the design

There was no mention of model releases and I am now in the process of resubmitting them with reference photos. Mine are rasters. I placed the original in illustrator, closed all gaps then re-placed it into photoshop to create a raster.

Thanks for the reminder, I forgot all about these.

Thanks, all. I have Illustrator, but don't 'do' Vectors and doubt they'd consider a test submission of three silhouettes, though I agree they'd be more useful as Vectors. I'm sure a designer would have a far better chance of being able to make the image a Vector than I would have.
Problem with taking the actual photo was a totally glary white sky, meaning I have to whack in tons of shadow fill, but even worse, the purple fringing in the photos are horrendous.
If they wanted to check I'd taken the original photo, I guess they could compare the camera number in the EXIF of the silhouette with those on all my submissions of the past two years.
I guess the only option is Alamy - 1 person, no MR, computer manipulation, isolated. I wouldn't expect these to sell on Alamy, but you've gotta do what you've gotta do.
Now to work on my isolations 
Tx again.

Sue, I will try to paste a link here to a shutterstock tutorial that I found real helpful and it makes the job real simple and easy.

http://www.shutterstock.com/tips-tricks/How-to-Create-a-Vector-Silhouette-in-Illustrator-421.html

When you are finished make sure you go to the image tab in photoshop and change the image to rgb so iStock will accept it.

Thanks, I'll give that a whirl for my own education - but I still think they'd be extremely unlikely to accept a test submission of three silhouettes. In photos, at least, they like to see variety in the submissions.