First of all, because this is a pet-peeve of mine, it's "Javascript"--not "Java". The two are not even related. Javascript is not a scripting subset of Java. However, VBScript is a scripting subset of Visual Basic (VB).
Looking at your code, I don't see a problem, but are you sure there aren't any javascript errors? If you are using IE, when your page loads, do you notice a small error icon in lower left? If you use Firefox, it has an excellent Javascript Errors Console window that you can leave open to see any and all errors--it's a great tool for development.
You can create a DIV like this:
<div id="waitdiv" style="position:absolute;top:100px;left:100px;padding:25px;font-size:20pt;">Please wait...images loading...</div>
Of course you can put any HTML you want inside the div and change the style to whatever you want. Then, in your LoadTrigger() function, do this:
document.getElementById('waitdiv').style.display = 'none';