There is no need for all the messing about with flags, macros, and conditional compilation.
Just put the declarations into a header file;
eg display.h:

extern U8 picture[]; // NB: Array bounds are not specified in a declaration

and then include that header wherever the variable is needed and in the file in which it is defined;
eg display.c:

#include "display.h"
U8 picture[8] = { etc, etc};

As I said before, including the header in the same file as the definition like this gives the compiler the chance to check that the extern declaration matches the actual definition - otherwise, the compiler will never know, and the linker may not spot it...