Some time ago our friend Maciej introduced us to a great card game called Coup. When we purchased localised version it turned out that instead of coins, it contains separate cards with "current balance" fields which you should navigate using a small marker. It's not very usable and isn't as cool as throwing 7 coins and yelling "I'm assasinating YOU!" ;) This is why I decided to design my own coins with our own faces on them. To do this you need to follow couple steps:

Take a silhouette photo

Silhouette photo is a photo you take when the light source is behind your subject and the contour is clearly visible. I found easiest way to do it, is to make your TV to show just white (plug it to a computer and show blank page), sit someone in front of it and take a picture.

Tweak your photo with Photoshop

• crop out (Image ⇒ Crop) anything which isn't white backround or your profile
• desaturate the image (Image ⇒ Adjustments ⇒ Desaturate)
• adjust levels so left arrow is on the right of the first peak and the right arrow is right before second peak (Image ⇒ Adjustments ⇒ Levels...)
  
• invert (Image ⇒ Adjustments ⇒ Invert)
• save as PNG file

Convert to vector

• use Vector Magic
• after uploading image, go to the first page of wizard (clicking < Back)
• set type of image to Artwork with blended edges
• set quality level to High
• set colors handling to Custom Colors and choose palette with only two colors
• download result as EPS
• convert to DXF using pstoedit:

$ pstoedit -dt -f dxf:-polyaslines\ -mm file.eps file.dxf

Customise SCAD file

• clone/download the repository
• copy your DXF file next to custocoin.scad file
• adjust profile_file, profile_scale, profile_offset_x and profile_offset_y
• render (F6) and export as STL

Dual color coins with one extruder

This makes the coins look much nicer and can be done even with one extruder. Simply pause the print when you'll see that printer started to fill the profile, and exchange filament to different color.

If you use Cura, there's a plugin which helps with this. Go to Plugins panel, select Pause at height, click V button and set Pause height to coin_width from SCAD file + layer height. This will create gcode which will pause and wait for you to swap filament.

Print your new, awesome coins!

and let me know how it went! If you have improvements to the SCAD file, fork and create pull request!