I recommend the Composer Study Companion Series by RaeAnna Goss. The Bach Issue listed below is a free sample, but she has many other composers available.
See the example for Bach below for how you might add a picture book as a biography for a composer.
Johann Sebastian Bach (1685-1750)
Composer Study Companion Series by RaeAnna Goss – the Bach issue is a free sample
Also see the Composer Study tab on the Kindergarten Page for more fun ideas!