well, keep up the good work. Even you have pr4, your current website traffic is low (over 1 million alexa) Try to optimize some keywords, especially your website name "design girls" and make it on top at google.
Congrats. But don't get satisfied and thinking that it will sustain. One of my site once have PR4 but downgraded to PR2, and it's not that I stopped doing with backlinks.
Great... Its really nice updates that u got PR 4 directly and good SE positions... I visited you site. it is also nice. simple and cool..... Best of luck dear...