There's plenty of places you could use images for free use, stealing somebody else's art... that's not right but you could try :P I create my own art using photoshop. It's very powerful, but if you aren't artistic just search for some. http://images.google.com/ can find some interesting stuff :)
A great place to get images for games is using the character and background maps for rpg2k. These are usually pics from snes and some playstation characters and setting. There are a lot of anime characters and other misc stuff you could use. Heres one place to try, it should be pretty easy to find more by searching there links. I am not sure if this is stealing, but these are made by game fans for use so... http://rpgmaker.gamesweb.com/faq01.html most of this stuff looks like it is for an rpg, but there lots of different stuff so, hope it helps:)
There is a site uGameDev that if for mac games. They have lots of free* assets for starting out. You just have to download stuffit expander ( yuk, makes me want to kill someone ) to read the .sit archives.
* Some assets are GPL some are uGameDev license. uGameDev basicly states it's free for Mac games so you might wnat to ask before you assume that's and a-ok for java development too.
I have no quams about stealing assets for development, asking and creditinging for a demo, but I would never use a stolen asset in a commercial/shareware game.
> I'm a decent programmer but a terrible artist. Where
> should I go to get textures and models to use in a
> game? Do I have to hire someone to make them, or is
> there an easier/cheaper way?
you can go check out http://eye.box.sk
they got all about stuff like that
I find that any program with vector graphic drawing
tools (such as Flash 5) allow even the crappiest artist
to make pretty cool looking images, due to stuff like
auto smoothening.
Photoshop and paintshop pro type programs can help you
create cool textures pretty painlessly, using filters
and whatnot.