I want replace

<*input type='image' src='http://f.static.flickr.com/23/b.jpg' onclick="window.open('http://url.drleeuk.com/to/?aBn&z');return true;">

with

<*img src='http://f.static.flickr.com/23/b.jpg'>

all in the site: http://www.foobar.com

<* = <

Can you give me a full .user.js file?

my email is ngn999#126.com .

thank you very much !

It's completely untested, but the following should work...

// ==UserScript==
// @name           ngn999's script
// @include        http://www.foobar.com/
// ==/UserScript==

inputs = document.evaluate('//input[@src="http://f.static.flickr.com/23/b.jpg"]',document,null,XPathResult.UNORDERED_NODE_SNAPSHOT_TYPE,null)

for (i = 0; i < inputs.snapshotLength; i++) {
  (thisInput = inputs.snapshotItem(i)).parentNode.insertBefore(document.createElement("img").src = "http://f.static.flickr.com/23/b.jpg", thisInput)
  thisInput.parentNode.removeChild(thisInput)  
}

thank yuo very much!
but
there are many images in my web page, and they have different url;
so...

// ==UserScript==
// @name           ngn999's script
// @include        http://www.foobar.com/
// ==/UserScript==

inputs = document.evaluate('//input[contains(@src,".jpg")]',document,null,XPathResult.UNORDERED_NODE_SNAPSHOT_TYPE,null)

for (i = 0; i < inputs.snapshotLength; i++) {
  (thisInput = inputs.snapshotItem(i)).parentNode.insertBefore(document.createElement("img").src = thisInput.src, thisInput)
  thisInput.parentNode.removeChild(thisInput)  
}

there is a problem:
could not convert javascript arg 0
why?

because you don't have Greasemonkey installed?