pictures in flashpoint need to be
created at a certain size. they can be stretched and squashed to any size afterwards, but the
original size needs to be a power of 2, so 4,8,16,32,64,128.... you get the picture... no pun intended
the only other reason could be that the description file is missing the sizing. it should look something like this
class main_bg : RscText
{
   idc = 100;
   style = ST_PICTURE;
   colorBackground[] = {0.3, 0.3, 0.3, 1};
   x = 0.6;
   y = 0.72;
   w = 0.38;
   h = 0.23;
   text = "graphics\fia.paa";
};
where x & y are the coordinates on screen, and w & h are width and height respectively.
congratulations, by the way