www.resexcellence.com is a wonderful resource for customizing Aqua. You can find icon sets, screensavers, application skins, program splash replacements, boot screens, software mods, themes, and tons of other modifications that will help you turn this OS into something unique to you.

If you are aware of other sites that fit this description, go ahead and post them here.

Another good site is InterfaceLIFT.

macthemes.net, aqua-soft.org, macthink.net

Site: Macthemes Forums
Notes: Just the best place to learn about mac customization. You also will can grab lots of icons, walls and themes.
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Site: Deviantart
Notes: The legend place for amazing wallpapers, everybody knows that place but for newbies who never visit..
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Site: Guikit.com
Notes: An exelent place to grab some icons and walls, there are widgets and recent customize softwares too.
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Site: Interfacelift
Notes: Great site to grab random icons, must have in your favorites.
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Site: The Iconfactory
Notes: From the creators of Pixadex and Candy Bar, this site also have a good icon collection.
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Site: Adiumxtras
Notes: Cool stuff for my favorite IM client
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More cool stuff:
Thanks to Aviel for give-me this new links

Site: widget : widget
Notes: Nice site with some custom icons, recomended by a friend.
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Site: Bartelme Design
Notes: Icons and Wallpapers
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Site: Bombia Design
Notes: Icons for you and me
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Site: The Yellow Icon
Notes: Great site with tons of amazing icons, one of my favorites source to grab quallity icon stuff
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Site: RimsHotDesign
Notes: Some good wallpapers and icons for your collection
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Site: RAD.E8
Notes: Icons and famous stuff with mac users, take a check out on her stuff
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Site: Mix The Pix
Notes: This site is other one of my favorites, really have nice icons for us
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Site: McDo Design
Notes: Elegant and sexy stuff made by a famous mac artist
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Site: Vanilla Soap Design
Notes: Another great random stuff what you must have to see
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Site: Ultradesks
Notes: Good stuff, icons, walls.. must have in your favorites
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Ok, being very noob here but....

How do you change the boot screen / login screen... in OS X86 10.4.3??????

Just not getting it, is it even poss?

Spanks

add to the list of cool macustomization sites http://www.pixelgirlpresents.com/

There should be 1 place for all

LIke a theme app

http://osx.portraitofakite.com/

http://www.mandolux.com

great site for wallpapers (many of them for multiscreen setups)

That is a very good question that i too would like the answer to if anyone is interested in telling us please?

While I was sufing, causing a fuss on the web, I found these cool wallpapers.........

I have them rotating every 15 mins on my desktop, very relaxing......

Enjoy, these are NOT my own work, congrats to whoever these belong to....

Posted this already on another thread, but I thought I'd post it here for more people to see ... here's the link: Change Apple Boot Logo

Haven't tried it personally though as I've got no time. Anyway, HTH

Look at Socksoff.co.uk: it's one of largest repository of links for wallpapers and gfx!

I remember that too...in particular, though, I remember the Friday the 13th "Phear" version of Mosaic...used to have a screenshot of the splash screen - anyone have that anymore?

http://psychopulse.deviantart.com/ - check it out!

Wallpapers

Icons

Yeah, Deviant Art is awesome for WallPapers!

I use InterfaceLIFT for icons.

Who needs anything else, if there's MacThemes? :>

Unfortunately, ResExcellence died a long, long while ago and it doesn't seem like it will ever be returning. A shame, because that was one of the first and best Mac UI customization sites.

at shadowspy ... wow that site is awesome ... but, how do you use it? I feel like a complete noob asking that question :X

Thanks guy, but i like the original aqua theme.

most of these sites in the original post are dead, sadly

Macthemes...

http://www.macthemes2.net/

GuiPulp:
http://guipulp.com/


iconpaper:
http://www.iconpaper.org/

Galaxy Gui.
Its Windowscentric, but it has an excellent 512x512px PNG Icon thread (and some other goodies).

Old Site
http://www.galaxygui.com/forum.htm

New Site (recent)
http://www.galaxygui.net/