you create a floortile in paint and draw it over and over again on the screen(using blitz) (if you mean for a 2d game) to create the floor for the room.
you can use other art programs like photoshop,gimp,paintshop,project dogwaffle
then you create other tiles such as doors,
and draw objects like keys,
then create a mapeditor in blitz to place stuff in rooms and save the room as a data file.
you can use other art programs like photoshop,gimp,paintshop,project dogwaffle
then you create other tiles such as doors,
and draw objects like keys,
then create a mapeditor in blitz to place stuff in rooms and save the room as a data file.