Yes indeed! Learners with a disability in one area may well have remarkable abilities in another. The terms used for such children are "twice-exceptional"  or “twice-gifted.” Some of the world's most famous thinkers and celebrities have been learning disabled and have excelled at a certain talent or skill. Einstein, Edison, Charles Schwab, the millionaire owner of the discount stock brokerage firm, the list goes on...  
 
I think it's really wonderful that your son is able to express himself through his artwork and it's a gift you should nurture and support as much as you can. To assess his abilities and devise an instructional plan that will work for him, you may need to talk with his school and get him tested. Understanding his unique needs and areas of strengths and weakness is the first step to helping him become a confident adult. The links below take you to articles that have a host of information on parenting a twice gifted child.  I hope it helps and good luck!
 
http://www.education.com/topic/gifted-and-learning-disability/
http://www.twicegifted.net/id4.html