Not sure if this has been posted yet or not...
Sony hasn't updated their custom theme tool, according to the US site that is. However, the JP site includes version 6.20 which has the + category icon. Note that they apparently don't want users removing the PSN logo. And, btw, it is in English (also in Korean and Japanese).
If you, like myself, aren't fluent in Japanese, click the right most button to agree with the eula and download.Code:http://www.jp.playstation.com/psp/dl/tool/psp_customtheme_tool_eula.html
If you're not interested in this tool, don't post. : )