|A croquis is used to try different garments and gauge if they suit your shape. I use the line/technical drawings of patterns superimposed on my croquis like this. If you are artistic, you can print out the croquis and draw your designs on top.
There are various instructions on how to make a croquis in blogs etc (google to find them), but I made mine using Photoshop. To make the croquis pictured I took a photo of myself in my underwear (that's the scary part, I hope no one ever gets a hold of this, lots of blackmail potential!) and deleted the background. I then ran the photo through a variety of Photoshop filters to get the a number of croquis that appealed to me. Here is another one I liked.
The effect is much softer and more flattering than a silhouette and looks better with clothing.
If you do not have access to Photoshop, there will be an online version soon where you can process your photos for free, I believe. There is also a free alternative at http://www.picnik.com/app#/home/welcome (NAYY). Upload a photo to try it out, then go to 'Create' and 'Effects' to try out different filters. The pencil sketch filter in 'Artistic' and the posterise filter in 'Misc' look like a good start to me.