I looked at all the themes and picked my favorites
 
Mercury light green
Mercsten blue meters (I love the blue meters)
Tungsten darker amber
Pro sonar 12
Tunkery light green


When Tungsten first came out, I thought I found my favorite theme until I zoomed in on an audio waveform that was selected. Especially when you really zoom in, you'll notice a big difference in the clarity of the waveform.
 
Mercury is far better, Tungsten is dark and fuzzy. I'd ask everyone to try this test and let me know if you agree. Tungsten is very dark instead of bright when you select the waveform and this is where the fuzziness comes from. I wish I knew an easy way to change this about Tungsten. This would allow me to try other Tungsten-like themes.
 
This was really the only thing with Tungsten that was a show stopper when it first came out. After I tried that I went back to Mercury. I like some things about Pro sonar 12 and may give it a try too. I'm going to give Mercury light green a good test next week.

I love the theme editor but boy is it time-consuming!!!
I am currently trying to complete a custom theme (complete, with all colours and icons modified), and use it as a model to  create some more. I'll make them available when they're ready. I'll need to complete them, then use them for some time and fix what doesn't look right (to me). Then let you have them when I think I've achieved what I was aiming for.
 
Yet, there are some flaws, lacks and inconsistencies in the tool. Some colors change several elements at once, and some items available in the editor are nowhere to be found in Sonar.
 
 
Here is a list of some items that I don't know what to do with, as I don't know where to find them in Sonar:
 
Global:
Dialog Box Banner Background
Alternative Text #1
Horizontal Sliders : Changes the sliders, but also the text color of the Sends text in the console view
Alternative Color #1
Drop Indicator
Quick Group
Enable/Disable Toggles

* * * * *
 
Track View :
Strip Background
Control Background
Track Icons Background
Control Icon
Slider Background
Track Name Outline
Track Inspector Background
Header Time Display
 
* * * * *
 
Track View / Track Pane :
Active track
Selected track
 
* * * * *
 
Console View :
Strip Background
Slider
Slider Background

I mainly use Mercury, but if my eyes get tired it's nice to switch to another theme. I don't make them. It's far too much work, and I've been happy with what some others have made.

The best Tungsten based theme for me so far is scook's 'Tuncury Light Green'.  The color choices don't fatigue my vision and everything appears clearly visible.
 
Don't get me wrong, there are several really good ones users have generously done and made available.

So I finally went in and explored the theme editor a bit. And now I understand why this 'feature' gets used so little and why so many of the user created themes I've seen uploaded are, to be kind, not exactly appealing.

How many books do you think would get written every year if word processors worked by forcing you to enter strings of numbers into a list, then save your work and print it before you could see if your codes form actual words and if those actual words make any kind of story?

I applaud the bakers for thinking to include a feature that allows you customize the colors of the interface. But until that feature includes a WYSIWYG style editor I predict very few will bother with it.

The fact that it's not WYSIWYG is definitely a pain, although you kind of get used to it. Open Sonar on one side, load a theme, open the editor on the other side, modify your stuff, save it, load your theme in Sonar, check the change, reload another theme so you can modfify and save your current work in the editor, make some more changes, etc.


One of the biggest difficulties is to know where to find a specific element (although most are logically sorted), and where exactly colors will apply.
 
Then it's also a matter of patience... and (good) taste. Spending hours of your time for ugly results is sort of discouraging.
 
The tool isn't perfect, but at least, there is one. We just wish it could get upgraded by the development team. That, and the staff view... Some day. Maybe.

I much prefer a dark GUI but that orange in Tungsten was exactly the wrong color for me, so I found a theme here called Dark Aqua and have been using it. I'd probably change a couple of things about it, but it's pretty good as it is and using the theme editor seems like more effort than I want to spend on it.

I recently tried my luck at creating a SSL 4000 theme, but I don't think I have the skills to get a good result. Didn't get much past the fader caps :)
 
Intrigued by inspired-by-consoles themes, Logic and reaper has a couple!
https://logicxcasoriathemes.jimdo.com/
http://forum.cockos.com/showthread.php?t=116647
http://www.houseofwhitetie.com/reaper/imperial/wt_imperial.html
 

I loved the IDEA of it, but 5 minutes exploring it revealed my limitations in graphic layout and vision while making it painfully clear that I don't have time to learn a new skill at the moment. Maybe someday :) 
Agreed about the comments of WYSIWYG; that would be brilliant.

Ok, actually I opened the theme editor and fairly quickly managed to change one of the things about the Dark Aqua theme that I didn't like  (the loop markers were too light to be seen easily if you also had a selection covering the loop area in the timeline). Likewise, if can easily find the items for the fx bin and send enable/disable switches, I'd darken  and increase the blue saturation of the enabled state a bit, it's a bit hard to distinguish from the gray of the disabled state. 

Digging through everything to find the right item is a little difficult though, I can see that building a theme from scratch would be a hefty task. So thanks to you guys that have done so and made your work available to the community.