I don't exactly know what it is, but I found some information on the web.
Gothic Lolita is sub style of Lolita and it's different to what we know as Gothic although we have similiarites. It's aesthetics make it a great fashion to explore and admire. Gothic Lolita is far more cute, less sexualised and generally looks like delicate dolls. This style can be traced back to the later 80s and orignated in Japan, the fashion developed and eventually attracted the attention of designers.
Gothic Lolita is characterized by two types of styles. First is the Gothic look which depending on the culture will range from the American black leather and lace punctuated by white face, black lips and eyeshadow. In Japan the Gothic look is more true to the the Gothic historical era which is better known as the Middle Ages. Lolita style is based on a sweet and innocent look that is sexualized as Lolita was a teen nymph. So the two styles when merged is still a sweet and innocent look based on lace, cute prints yet in a Gothic style - think babydoll hats, big eyelashes, soft makeup... it can be black velvet, heavy silk or taffeta fabrics or it could be pinks, baby blues, baby greens. The American Gothic Lolita look is a bit slutty in my eyes compared to the Japanese Gothic Lolita style.
I would suggest picking up the Gothic and Lolita Bibles from Amazon. Yes the Bibles are in Japanese and yes the Bibles are expensive. I buy mine at Kinokuniya is Seattle. I also use to buy from Amazon Japan but stopped when they jacked up their shipping prices and got rid of SAL in favor of EMS... I wasn't paying $30 US in shipping on a book! I also use to buy from CD Japan and I know the latest Bible is #43 and it's 1300 yen (about $15 to $16 US), shipping should be either 500 yen or 700 yen making it about $25 US after shipping.
What you posted in your post above is more American Gothic rather than Gothic Lolita. Like I said, Japanese Gothic Lolita - which sets the bar on Gothic fashion - is more innocent, baby doll looks rather than slutty, boobs hanging out. I would also suggest deciding what version you're going after American or Japanese. I think more people - least among the circles I tend to be in - are of the belief that Japanese Gothic look is more true than American. Of course there is the British Gothic scene by that is totally different as well. It was the Japanese Gothic & Lolita scene that really popularized it as being a true fashion in the 21st Century.