Here's an interesting look at the Jihadist Art Therapy Rehabilitation program from a PBS special:
According to this Psychology Today article, you can't really call it "art" because that is derogatory and has a negative connotation. There are other restrictions, too:
Islamic law prohibits the depiction of people or animals in artwork so drawings are generally abstract, at times integrating text from the Koran or other sources. The calligraphy and depictions of sunrises and flowers do not really reflect the darker emotions confronted in treatment and are images Western therapists might not expect to see. In fact, some might define the content of their artwork as being "in denial" of the crimes committed. With these individuals, it's the process of making art and Alyami's careful interventions to help these men examine the consequences of past actions and discussion of their art that are the core of their art therapy.
Two of the four Detroit plotters were graduates of this program. I don't think it worked too well for them.
According to the video, most participants in the program complete a two month stay. The doctor in charge of the program says 208 completed the program and only 5% have relapsed. He might need to adjust those numbers now.