[O] extending automatic screenshot insertion

[Aditya Mandayam]

hello,

i would like to extend the auto screenshot method described here:
http://comments.gmane.org/gmane.emacs.orgmode/33770

first: a way in which i can be prompted to enter a filename instead of
having a random string
second: a timestamp be appended after i have entered the filename
third: to specify somehow, the dimensions of the bounding box of the screenshot

how can this be done?

thanks,

a