you know a new album of new tunes would be great, i was also thinking that a new album of totally motorized cover tunes would be pretty cool too. I'm sure Lemmy and the boys have their own favorites, but i might suggest a few myself like:
Cities on Flame - the classic heavy monster from BOC's 'On Your Feet or On Your Knees' live album.
Eve of Destruction - classic anti-war by Barry McGuire.
Barbed Wire by Link Wray (also known as Run, Chicken, Run), they could do it as an instrumental or Lemmy could add lyrics (maybe "Run, Bastard, Run"!).
Dio - I Speed at Night.
Twenty Flight Rock - was that Gene Vincent?
Bangin' Man - Slade.
Ballroom Blitz - The Sweet, hey what the hell why not.
Modern Times Rock and Roll - Queen - pretty already in the Motorhead style anyhow.
I'd suggest a Ramones song but they've already recorded RAMONES twice already.
My Baby Left Me - Elvis & others (actually thinking more of the live Slade version).
Seven Drunken Nights - traditional.
Mean Woman Blues - Roy Orbison.
I'd hesitate to suggest The Beatles, who've been done to death in covers, but there's always I am the Walrus.