First person wanting to use tag clouds and the download gallery! And it doesn't work :(
I looked at the source code for NGG 1.9.13 and it does actually accept a template parameter, which it duly passes on to the
nggTagCloud() function; that function does absolutely nothing with it, so we're out of luck. I also looked at NGG 2.0.33, which passes the template parameter to some other display types, but it too drops the template parameter on the floor when displaying tag clouds.
So I'm afraid I have to say: you're out of luck there. I'm going to have to basically rewrite the
tagcloud shortcode to extend it for templates, which I'm not going to do this year (maybe next year if time permits).
What you can do, if you don't have too many tags, is use the extended version of the
nggtags shortcode that I wrote as
nggtags_ext as this does support other templates. Like this:
[nggtags_ext album="beach,birthday,barbecue" template=download]
That will create a virtual album with three virtual galleries, one for each tag. If you don't have too many tags, that's a way you can do it. But I realise it isn't the best solution, so I'll mark this down as work to be done.