There are undocumented features in all the widgets now to allow users to customize things a bit.  Adding this before your widget <script> tag will give you access to them:
<script language="javascript">
window.centovacast = {
	options: {
		recenttracks: {
			poll_limit: 60,		// number of times to update the tracks list before stopping
			poll_frequency: 60000,	// how often (in milliseconds) to poll the server
			track_limit: 0,		// number iof tracks to display (0 to display all on file)
			show_covers: 1,		// 1 to show covers, 0 to hide
			buy_target: '_blank'	// '_blank' to open in new window, '' to open in same window
		}
	}
};
</script>
Tweak as needed (in this case, set show_covers to 0) to achieve whatever effect you're looking for.
As always, the overall appearance is configured using CSS.