Thats the only proper custom decal site I know of unfortunatley, but theres loads of off the peg type options that allow you to make up a design yourself, Motrax do decal kits and things
http://www.motrax.co.uk/ sure there are dealers in Belgium. Alternatively try ebay always loads to be found there.
If you look round the all out graphics site there are loads of examples on there and if email them they will do mock ups for you and even your designs (got a mate thats handy with art work?). Blimey I sound like a sales man for them! I will give them a try when I get my SV but if you let me know how you get on with if you decide to use them that would be great.
Cheers,
Pixie