Okay I got this.
1. Take your bitmap and preferebly make it black and white (if possible).
2. Download Inkscape and open your bitmap in Inkscape. (select embed and not linked if it asks).
3. Select your bitmap in Inkscape by clicking on it (you wouldn't have guessed that would you

)
4. Press Shift+Alt+B (or Path-> convert Bitmap in the menu). This will open a window with a lot of parameters, just click ok.
5. Now Inkscape should have converted your bitmap to a vector image which lies ontop of the bitmap. Drag the vector image a bit to the side and delete the bitmap.
6. Now save your new vector image as .svg somewhere.
(if the convertion didn't do good enough edit the parameters until you get a better result or edit the vector image manualy)
7. After that, follow this guide (open the pdf):
http://cleversomeday.com/inkscape-dings/This guide explains how you can edit an svg font and how you can convert it to a ttf. (Note: skip the whole xml editing thing, it is useless)
8. Once you have your ttf install it and open your PCB.
9. Place a string on it and select "True Type font" in the string editor.
10. Now select your font and write as string the glyph with your logo on it.
11. Set the appropriate height to scale your logo (the height won't match the actual height because you will probably not use 100% of the given glyph space).
12. Have fun!
I did the whole thing myself in about 5mins.
I attached the different steps as a reference.

