A good suggestion would be to have an admin panel for users that aren't that keen on editing stuff. Having the gallery pull images from categories and all is great ... but i would rather point it to a special directory and only have special images for the slideshow.
This is because most slideshows already do the other things but none come with an actual intuitive (read: newbie friendly) and simple admin interface where people can just upload images to the slideshow *AND* where the plugin automatically (please) resizes the images, crops them etc.. to fit whatever "viewport" one want;
XHTML:
<div id="topimg" class="slideshow">
<span><img src="1.jpg" alt="Alt-text" title="Description" /></span>
<span><img src="2.jpg" alt="Alt-text" title="Description" /></span>
<span><img src="3.jpg" alt="Alt-text" title="Description/></span>
</div>
CSS:
#topimg {position:relative; height:300px; }
#topimg img {position:absolute;z-index:1;}
#topimg span {position:absolute;z-index:2;background:url(cool-borders-in-a-transparent-png-24.png) no-repeat; }
One should ofc. have the option to have all images linked to "x" where "x" can be a post or whatever one chooses (this would also make the whole thing a viable choice for a feature content slider - especially if it was newbie friendly / non-tech friendly). And focus on it being compliant with XHTML Strict or even better - let one modify the output for ones needs.
Another suggesion is to have all the tech-stuff in one area and all the newbie-friendly stuff in another. That way clients doesn't have to get über-confused with stuff like auto-resize, cropping etc.
Good luck!