Mmm, well. There's a mini-map script created by Wortana, but I don't think that's what you're looking for. To show an image on a button press is pretty easy. Set up a common event, make sure it's set to Parallel Process and give it a switch. (Make sure this switch is turned on sometime so that the common event actually works. Best to just keep it on all the time.) In the common event place a conditional branch that checks if the player is pressing a certain button. Make sure it's an unused button. If yes, then show the picture of your world map. Then inside there loop another conditional branch checking if the player is again pressing either the same button or a different button. If yes, then break the loop, remove the image and it should start the processing back at the beginning.
This is a bad idea if you're using an ABS since it'd be possible to accidentally press this button during combat. Not good.
Uh, for checking your position on the picture is much more complicated. Check this:
http://rmrk.net/index.php/topic,28850.0.htmlIt's a way to create a mini-map using images, however, you should be able to easily convert a tiny image that appears in the corner into an image that fills the entire screen. Of course, this image would be what you pull up from the common event.
It'll be tricky to get the two working together. I don't think you'd be able to do it and I haven't worked with VX in a while to tell you off the top of my head.