Almost there.
<marquee direction="right" align="middle" behavior="alternate" SCROLLAMOUNT=150 SCROLLDELAY=0 >ROCK ON! ROCK ON! ROCK ON! </marquee>
would be
<marquee direction="right" align="middle" behavior="alternate" MARQUEE HEIGHT=50 SCROLLAMOUNT=150 SCROLLDELAY=0 >ROCK ON! ROCK ON! ROCK ON! </marquee>
You can put the COLOR, FONT, and SIZE tags within the marque code also.
And as BobBrazeal mentioned, the link he posted would help out with the image size in signatures.