I've been messing around with exactly this kind of thing. Though as part of it I want to move the image declarations to CSS so that size, filetype and various other things can all be altered, even on a user by user basis.
You can see some ideas and work in the Moodle Docs wiki here:
I'm hoping to have the CSS support for this (just adding a few CSS classes here and there, nothing disruptive) added in time for the 1.7 release.
Without really understanding what kind of feedback you want, Glossary and (in 1.6+) Database seem like they might be useful.
These allow you to browse or search through many entries/records and leave comments. The feedback is less structured than Choice/Quiz/Questionnaire but the access to the individual entries is more non-linear/random-access.
If you are thinking about replacing the icon then i'd suggest something:
One I like is the flickr default buddy icon:
I feel that if you do that (like the current Moodle default does) you subtly encourage people to a) replace it with something uniquely identifying and b) use it somewhat correctly i.e. a recognisable passport-like facial portrait, while not alienating anyone. Note that even people like me (and Harry above) that use a bit of artwork, use something with a face. Even the cats/cartoon characters have generally shown their face to the camera.
As an aside, Scott McCloud's Understanding Comics has an interesting section about how the abstraction of the smiley face requires engagement by the viewer to fill in the details in a way that more realistic representations of a face don't. There's also the consideration that the shadowy, faceless silhouette that is often used in this context is fairly ominous. I think Martin mentioned that he'd intentionally avoided using such an image.
And for the record, I believe the original Moodle image is of a smiley faced cake. I find this all ironic as I (as a child of the 80s) always connected the smiley face (i.e. on its own without it being situated on a cake/tablet shaped object) first with the drug subculture of the 60s and 70s and then the Acid House scene of the late 80s (possibly just a british phenomenon) but since Wal-mart (ASDA in the UK) is currently trying to claim ownership of the symbol and every instant messenger/email client/forum in the world lets you insert such smiley faces (e.g. ) then obviously those connotations are no longer current in the mainstream population.
Did you follow the testing procedure outlined in that article and see images being downloaded each time? I'm surprised that a browser would fetch an image on each page. If anything I have the opposite problem and often have to force refreshes to get images to update. And if the browser does try to fetch an image (or any other resource) a second time then, if all is going according to plan, then the server should say "no need, the copy you have is still fresh".
I honestly don't know that much about this area, but what I read in that article surprises me.
I think the short version is:
If you modify Moodle code and sell or distribute that code to people outwith your own organisation, then you must also make the code changes available to anyone you sell or distribute the code to under the terms of the GPL (which in turn allows them to give away or sell that code).
Note that hosting a website and allowing people access to it is not the same as distribution. Some people see this as a loophole in the GPL (which wasn't written with web applications in mind) and it may be changed in the next version of the GPL.
Content loaded into Moodle by you or anyone else is not covered by the GPL, any more than an email written in an open source email client, or image created with open source graphics software becomes open source.
Final nitpick: Public Domain is a precise technical term that doesn't really apply here. You still own the copyright to your changes, it's just that in return for being allowed to build upon the rest of Moodle you're being required to specifically grant other people the rights to do certain things with your code too.
The usual I am not a lawyer disclaimers apply and it's probably best to get a few opinions before believing anything about open source licencing. It's not that it's complicated as such, but it's quite novel to most people and there's a lot of disinformation about.