I could use some help on determining the proper way to mark up images...

This topic came up in the past, and I chose to do things a certain way, but I know in another recent thread of mine, Paul O' mentioned that I should make some changes (of which I don't remember).

Here is some sample code...
HTML Code:
	<div id="boxArticleIndex">
		<h2>Small-Business Articles</h2>

		<!-- Summary #1 -->
		<div class="articleSummary">
			<h3>Postage Meters Can Save You Money</h3>
			<div class="image">
				<a href="<?php echo BASE_URL; ?>articles/postage-meters-can-save-you-money">
					<img src="<?php echo BASE_URL; ?>images/PostageMeter.png" width="170"
						alt="Picture: Postage Meter.  Credit: John Doe, Wikimedia Commons."
						title="Picture: Postage Meter.  Credit: John Doe, Wikimedia Commons." />
I think Paul O' was saying to drop the word "Picture" and maybe even the whole alt tag?

This much I do know, however...

Because I am using pictures from Wikimedia Commons, I need to give credit to the author of the image. However, I do NOT want to have to "advertise" this information below the picture, because 1.) It takes up precious space, and 2.) People may perceive using open-source pictures as "cheap" or "unprofessional".

It seems to me I used what is above, because it would give due credit to the author when someone hovers over the image OR for visually impaired users, screen readers would announce the Author.

Hopefully there is a solution that meets my needs, is accessible, and give due credit to the generous authors sharing their work with me?!