Hi weldmetal12, i'll try to help in this, although my understanding of French is very poor.
There are some options here:
"Front" in French means something like "combat zone", i think. So it could make a reference to the "Battle of Ardennes", which happened in WWI.
See
https://en.wikipedia...of_the_Ardennes
But there's also another battle which could be translated with the same name, but this one was in WWII, although it seems this one is known as the "Battle of the Bulge".
See
https://fr.wikipedia...le_des_Ardennes and
https://en.wikipedia...le_of_the_Bulge
And then we have a film from
1965 called "Battle of the Bulge", based on the WWII battle.
See
https://en.wikipedia...he_Bulge_(film) and
https://fr.wikipedia...le_des_Ardennes
Being the track based on
1967 maybe it was just film advertising. If i'm correct, Isle of Lewis is in Scotland (i'd bet so as you're talking about making a painted tartan). If your worries are that something of those battles has something related with Scotland, i think you are safe, i've been reading about them in English, Spanish and French and nothing related with Scotland arises.
If it is appropiate to your son, i'll leave that decision to you

, but i think there is no problem. Moreover, think that your intention is to paint a beautiful corner of one of the most beautiful racetracks ever. Explain to your son that it has nothing to do with politics but motorsport. And if it makes reference to political stuff, well it's something from the past and there's nothing we can do to change the past, just learn from it. That text belongs to the old Spa, and the meaning you should take is that it's a banner in Eau Rouge corner.
Conclusion: In your situation, i would paint it with no doubt, but again, i'll leave that decision to you.
Hope this info helps buddy
EDIT: I thought you were talking about some sign at the side of the track, but i saw a video and a picture and the text is on the tarmac and it prays "Front des Ardennais en colere" so i would discard the film advertisement. That sentence is showing annoyance, so definitely it's some political stuff. Again, is part of the track, this is about motorsport, so i see no problem with that text being there.
Edited by TurboMan, Oct 12 2017 - 02:10 PM.