filename<tab>caption style file, it'll add a caption to the images
on the index page.
+If both width and height are specified then it'll be resized to the bounding
+box that contains it.
+
+If height is specified without width then the bounding box will be 100xHEIGHT
+for icons and 400xMEDIUMHEIGHT for the medium sized image pages
+
The following environment variables can also be used:
TITLE
the title of the gallery
WIDTH
the width to make the icons
+ HEIGHT
+ the height to make the icons
+
MEDIUMWIDTH
set the width of images in the medium size pages
+ MEDIUMHEIGHT
+ the height to make images in the medium size pages
+
BPGALLERY_THEME
set the theme to use (described below)