The capital of Andorra wasn't a great destination in 1972 and has deteriorated since then. The term "outlet mall" gets tossed around. The scenery in that area is certainly worth seeing, though. You can go to ViaMichelin.com and zoom way in to see the most scenic roads highlighted in green. Slightly off the route that skirts Andorra-the-country to the west is La Seu d'Urgell. Puigcerda (poo cher DAH) is essentially right on that route. Both towns (not tiny) have attractive architecture. There are several old, small villages along highway N-260 between the two. Note that the Cerdanya Valley can be blisteringly hot in the summer. If you have a bit of extra time you could take the short detour northeast of Puigcerda to Llivia, an old Spanish town completely surrounded by France. The small towns in this area don't seem to get many tourists; I'm doubtful that they have much in the way of traditional sights--maybe an old church or two. Puigcerda does get visitors, as does La Seu d'Urgell.
If you need an earlier stop, I can recommend Foix.
On the other route you have Toulouse, a city of considerable size with lots of very attractive pink-brick architecture and quite a lot of sights. For both those reasons, it's not necessarily a great place for a quick stop, but I liked it a lot. I'd say it would be worth it if you could give the city at least six hours.
Albi, as previously mentioned, is also worthwhile, but it's off the direct route.
Beyond Carcassonne is Narbonne, to which I took a quick day trip a few years ago. It seemed like a promising place to spend a bit more time. Further south is Perpignan. It's a bit less polished-for-tourists than some other French cities, I'd say, but I liked it. The Palace of the Kings of Mallorca is worth a visit. I remember it as being basically unfurnished, but my memory has been known to fail me on points like that; I'm not a palace person.
Collioure is an attractive town. If you like modern art, I recommend the Museum of Modern Art. It's not large.