This is probably due to the spectrogram processing uses a WAV as input file, thus I made it transcode the audio into WAV (which takes quite a lot of space).

A possible solution would be to investigate the possibilities to create spectrograms from either the source format or the "medium" audio/webm format.

An image can have transparent background, and foreground of a color close to the theme’s page background color. A GMG instance can contain images of different colors, so choosing an instance with an appropriate theme for an image is not a good solution. ;)

It would be good to allow the uploader choose a background color for (one or more):

• the area behind the thumbnail;
• the area behind the thumbnail and some around it;
• the whole page or a little less;
• the thumbnail to be generated.

When the words on the prev/next buttons are of different length, the buttons can sometimes have a different height (e.g. one line or 2 lines): ​https://mediagoblin.com/u/cwebber/m/mediagoblin-0-1-0/?lang=ru

Can they be forced to have the same height? They seem always to be arranged horizontally anyway.