Search the University of Illinois' reference section geared to enriching the classroom experience. The site -- http://urbanext.illinois.edu/bhm/historyforkids.html -- offers links and a "Teacher's Guide" to using resources. The guide, http://www.education-world.com/a_lesson/lesson252.shtml, offers a variety of approaches for what might be depicted in the mural, including a regional slant.
The First School website offers suggestions and themes geared to kindergarten students: http://www.first-school.ws/theme/educational-resources/black-history-month.htm. Site links range from biographies of musicians and scientists to a link for a regional culture of the Gullah community in South Carolina.
Education.com has a section titled "Kindergarten Black History Month Activities" at http://www.education.com/activity/kindergarten/black-history-month/. This site has an age-appropriate arts and crafts learning resource that teaches historical and cultural topics through hands-on projects that could be added to create a three-dimensional mural.
Connected has a site called "Best Ways to Teach Kindergarten Students About Black History Month." The site, http://connected.waldenu.edu/curriculum-resources/lesson-plans-and-class-activities/item/1173-best-ways-to-teach-kindergarten-students-about-black-history-month, has a multi-approach source to exploring Black History Month for kindergarten classes. They also have a resource link for further exploration.