Okay, here's my take on the logos. All of these are my personal opinions, so it's just a suggestion :).
* vector art instead of bitmaps -- simple clean logos are the best
* proper font -- The "Doom" font for DoomRL, the "Diablo" font for DiabloRL, "Anything you want" for Berserk, "Aliens" for AliensRL for Valkyrie and Neko it's kind of open, but rather modern fonts and not classical.
* simplicity of the design -- the less but more accented the better
* PNG instead of JPG. JPG makes a mess out of fine pixel-work D:
* Some ASCII signs, or any suggestion that it's a roguelike would be cool
My takes on the look of the logos:
DoomRL - The original Doom logo with the RL letters. Maybe just a hell landscape instead of characters, maybe use Derek's sprites for the logo. Maybe some ASCII ( doomlogo2.jpg looks the best IMHO, but the Bevel should be smaller, and the letters looked better when they were gold (better contrast) )
DiabloRL - here I'd definitively go for the Diablo logo with an RL over it, and a part of a ASCII map with an @, some floor and a few monsters below and in the background.
Berserk! - there's only one thing that can be on a Berserk! logo, and that's the mark of Sacrifice ;).
AliensRL - should probably be just the name similar to the title-page, on a black background.
Valkyrie - I don't have any particular ideas here, but probably only some symbolic art, not images. Colors -- black and blue
Neko - as the name implies the logo should be a cat >^_^<. And I'm definitively sure it should be Kuro-neko-sama from Trigun -- probably just his characteristical face. ( for those who don't know what the hell am I talking about :
http://hagure-metaru.net/wordpress/wp-content/uploads/2007/05/kuroneko-sama.jpg )
P.S. Of course everyone is welcome to try doing logos :D
