@nppbc – My apologies, I was thinking a different item where there is an over-ride for the thumbnails.
This may be more complicated to accomplish with a TagCloud display. IIRC, you wanted to have portrait orientation for some of your thumbnails, and now you want them to be uniform when you use the TagCloud display. As it is, I do not believe it is possible to have both.
You could try the following: under Gallery > Gallery Settings > NextGEN Basic Thumbnails … override the Thumbnail size and ensure set fix dimension is set to Yes.
Now go to each gallery that has images you will be showing in the TagCloud displays and either select the whole gallery or the specific images and generate new thumbnails for those images.
Next, clear your image cache … then have a look at the gallery.
Otherwise, this may need to be treated as a Feature Request to allow TagCloud displays to over-ride Thumbnail image sizes (if it applies to the display as selection under the Customization panel).
– Cais.