Gilles,
I use Font creator from
http://www.high-logic.com. It's the only one I know that allows you to paste bitmap graphics and then resize them to fit the character space. Try out a few of the demos, I bought mine years ago and have not bothered to update it.
Jeff
2-Xeon X5680 @ 3.33, EVGA SR-2 Mobo, 48GB DDR3, GTX 580 3072MB, 16TB Attached Storage, Win7, Vegas 11 x64