I have several 450 element character arrays (storing bitmap data to display on lcd screens.) I would like to put them under a header file and #define them, but
Well... you certainly don't need to use a define. Just add them into the header as const, static arrays.
/* prevents multiple, redundant includes */
/* make sure to use a symbol that is fairly sure to be unique */
#ifndef TEST_H
#define TEST_H
/* your image data */
const char image[] = { 1, 2, 3, 4, ... };
#endif
Also, if you want help on a compilation error then you should post your code.