Right now I can have around 600k files, a very comfortable number for the next months/years.
I see. That's tiny 
For comparison: a "normal" filesystem on a 1 TB disk has 58 million inodes (which means it could handle that many small files).
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You know that hosting services talk about unlimited, but there is always some kind of limit. I preferred to have unlimited disk space and bandwidth.
I learned a long time ago to stay away from "unlimited". I prefer to know what I get.Quote
So entering 800k files now would require a new server upgrade. And I didn't want to do that now. But, I'm checking several options that can make everything viable, without having to do a new upgrade. Therefore, what I ask now is patience to be able to support this type of action. I am studying what I can do to accommodate these images.
I used to use shared hosting, until my last one disappeared. Since then, I've become much more comfortable with VPS servers, which in general give better specs for money, but don't come with a pre-installed selection of scripts.