How about allowing named arguments for common sizes, like IAB (http://www.iab.net/iab_products_and_industry_services/1421/1443/1452 http://www.iab.net/iab_prod

How about allowing named arguments for common sizes, like IAB (http://www.iab.net/iab_products_and_industry_services/1421/1443/1452 http://www.iab.net/iab_products_and_industry_services/1421/1...) or common display sizes (http://en.wikipedia.org/wiki/File:Vector_Video_Standards2.svg http://en.wikipedia.org/wiki/File:Vector_Video_Standards2.sv...)? So you could do, http://dummyimage.com/skyscraper http://dummyimage.com/skyscraper instead of http://dummyimage.com/120x600 http://dummyimage.com/120x600