Question about themes

[fishnmagician]

I have been looking around here and there are some great looking themes. I have downloaded a few and put them on my phone and love them. My question is, I have wm 6.5 on my phone and under the today settings there is a list of all the "themes" on my phone. Is there a way to add the themes that
I have downloaded from here so that they will all show up there and i can just click on them and they will just go on? Right now the themes are .cab files and i just install them but it would be easier if they were already installed and i could just switch from theme to theme. Or do the themes have to be put in when the rom was being made in order for it to work like that? Hope I made enough sense out of this for someone to understand.