I do not believe a comma is necessary in this sentence at all. In fact, if you were to insert a comma after the word grazed (as you maybe tempted to do) it could change the meaning of the sentence. If you meant the lions were oblivious of the presence of the gazelles, you would insert a comma after grazed. But if you meant the gazelles were oblivious of the presence of the lions, you would leave the comma out.
Because there are two topics – fashion and design – the verb should be the plural. The sentence "Fashion and design has always interested humans" implies there is only one topic."
