What suggestions can I give?- Anything eg:
What features do you miss the most?
Are there annoyances?
Anything you think should be focused on more?
Other games to have a look at?
Something other games solved better?
Found fitting free and open content on the web?
You authored and submitted fitting content somewhere on the web?
What content may be useful?- *Original* mech-models
Other vehicles (military/civilian)
Dropships and bulky Spacecarriers
Maybe foot-soldiers or workers
Which Content License?
CC0 
, CC-BY 
, CC-BY-SA 
GPL, LGPL, APL, -NC/-ND, proprietary game art What's the workflow for content integration?- 1. Submit your quality art to http://OpenGameArt.org or to similar open content pages.
(unpublished art will be ignored)
2. Make a suggestion here.
3. It will be reviewed.
4. If it suits the project's needs it may be integrated eventually.
Why didn't my suggestion lead to an integration?- Integration is usually not planed long ahead - it just happens when it happens:
A) There is a chance that a model will be included later at some point as it fits into the development process.
B) Your suggestion may still influence the project in some way.
C) There may be License, Copyright, or Resemblance problems.
D) It just isn't the right time.
E) Sometimes a model is just not fitting at all (quality, style, personal taste).
Please don't be disappointed and take the chance to excel.
Why shall I upload my art to http://OpenGameArt.org anyway?- Because this way your art is already archived and usable for all open game projects, too.
Eventually someone may find your art there and say: Yeah just what I needed.
Later versions of OpenGameArt will support tracking versions of art while they are work-in-progress.
What are the quality standards for content?- Currently just personal taste - look at what's already integrated and make it better.
Textures aren't needed at the moment because there is "auto-texturing" going on.
A textured model may improve your chances as it may become even more useful.
What are those [ ] braces in the forum topic titles?- Within the braces you can see what's the state of the topic.
Is the content already integrated or are there problems, like a resemblance with proprietory content?
Is it an ongoing (open) discussion or is it a bug that was fixed (implemented, closed)?
Now, what are you waiting for? 