1. An article on this was in LTR some time ago, check it out at:
http://ltrpub.com/insideltr/articles/article_27/article_27.htm
There has been some discussions and examples of it here as well though, check out the last entry (I think there are others here too, just search for contextual menu or po-up menu):
http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RPAGEID=135&HOID=50650000000800000084640000&UCATEGORY_0=_49_%24_6_&UCATEGORY_S=0&USEARCHCONTEXT_TIER_0=0&USEARCHCONTEXT_TIER_S=0&USEARCHCONTEXT_QUESTION_0=contextual+menu&USEARCHCONTEXT_QUESTION_S=0
2. Color the border and background transparent. Just choosing background color and foreground color to be transparent and then using the paint tool does not work though, instead - hold the paint too
l over the border, right click to get the color palette, move the cursor above the T (transparent) then press F...and then B, now the border should become transparent. Paint the background transparent...After doing everything transparent this way - import the pictures into it.