Hi Benoit Robert , we always like to add a little surprise to our packages!  Over the years we've had many different designs (I can't even remember them all)-- usually we get a batch of bricks, have them printed, then put them in customer boxes until that supply is exhausted.  Sadly, we haven't kept a full collection ourselves!  😣

A little piece of trivia: two years ago we worked with a brick printer who had a bunch of 1x8 bricks in orange (our signature color!).  We received these and sent them out in orders.  The funny thing is, technically 1x8 orange bricks don't exist!  You won't find them anywhere-- not on Bricklink, not anywhere.  So how did our printer get them?  He believes they were from the days when LEGO employees working in LEGOLand parks could order any brick in any color from the factory, for use in model building for the parks.  So these are very rare indeed!  If you have one of these 1x8 orange bricks from us, consider yourself very lucky!