I use the this.ClassResourcePath for Web Part images. If deployed
locally, the images  will be placed into a subdirectory of the
wpresources directory under the home directory of the IIS Web Site. If
deployed globally, the images will be placed into the virtual directory
_wpresources in the 60 hive.

This works great, but remember to include your image  files in the manifest.xml and set the build type to "content" for the images.

addition to the manifest.xml:

<ClassResources>
<ClassResource FileName="image.gif"/>
</ClassResources>

Thanks. its Great!.. I also have tried to place  the image  folder in
60\template\images folder.(/_layouts/images/myImagefolder/), images
works fine. but some reference  javascript file also placed in
wpresources folder. it works fine. only drawback is need to deploy as
seperate exe/run application. Is this approach is not recommended or
we have to stick to the approach which todd has mensioned!

Yes, it works well for JavaScript, XML, CSS, images, etc. Any external
file-based resource that your Web Part may need.

Yes, I would not recommend deploying your images  anywhere in the 60
hive. Use the wpresources directory which is a sibling to the root of
the 60 hive. That is its intended use. And as you say, deploying
anywhere else requires an additional deployment.

You will read in some documentation that you can construct your own
ASP.NET applications in the _layouts directory. I also recommend against
this. Remember, the 60 hive is fair game for Microsoft to alter, update,
replace entirely, spindle, fold, mutilate, etc. They warn us not to mess
with most of its content. If we do want to change the way things work we
should create our own subdirectory as you suggest.