While you could create new from scratch it is not needed. There are something that you can do that is much easier, and that probably is more needed: Adding buildings.
Placing generic buildings can help a lot to go from a featureless flat airport to something that looks at least a little bit better. I recommend that you look into placing generic buildings with the UFO and submitting them to the scenery database. That way you will not just to get to see them yourself, but you improve the scenery for everyone else as well (through the default scenery, TerraSync).
I have just taken a quick look at the Moroccan airports in OpenStreetMap, and it seem that most of them are well mapped which might help a little as you will need good reference. You will also need to look for good reference photos of where buildings are located. (At some point you might want to model buildings like airport terminals, but that is for maybe later).
To get going have a look at this scenery database website page:
And also this article on the FlightGear wiki:
You do not have to jump in on it right away, but give it some though the next couple of weeks.
Something you could possibly try later on, and something I have not tried myself, and that seem to be a little bit more work and require a little bit more coordination with someone with commit access to the FGData repository, is to improve the textures. Probably the best way to work with that is by creating procedural textures. Procedural textures requires a bit of adjusting and are set up using a few textures and writing configuration files that tell the rendering engine of FlightGear how to use them. However, procedural textures do look a lot better than single repeating photo textures, and are much less prone to patterns repeating off into the distance (also known as "tiling").