More information is needed. All are your images the same size? if so what size. you cannot control the size of the montage except by spacing between the images. so to get the final result, you need to resize, but that may still be off some unless you are willing to distort the image so as not to preserver aspect ratio.
try
montage $name -tile x1 -geometry +2+2 -resize 728x90 output.jpg
if you want exactly 728x90 and are willing to distort some, use !
montage $name -tile x1 -geometry +2+2 -resize "728x90!" output.jpg
For composite try
composite foreground background -gravity center -compose over result
or
convert background foreground -gravity center -compose over result
see
http://www.imagemagick.org/Usage/compose/#compose