These are the covers I made for The Enchanted Attic series by L. L. Samson and published by Zonderkids.
Three kids find an abandoned attic that used to be some sort of mysterious and magical lab. There they are able to bring characters from the classical books they read into reality and, of course, they get into trouble for that.
Facing the Hunchback of Notre Dame
Saving Moby Dick
Dueling With the Three Musketeers