It's not OK in the sense that it is a spec violation, at least. Some clients have images that load in-line on mouseover or click, which isn't a spec violation. You could do that with HTML.
If people specifically sought out your client because it automatically renders images inline, who could be bothered to get upset about a "spec violation"? The author of Gemini? What would he be able to do?
Probably someone would submit a PR complaining. A lot of folks in the gemini community are strict about the spec. In my view, they would be justified in doing so — I think adherence to specs is important in any domain, not just gemini.
Drew himself threatened to block a Gemini agent that fetched /favicon.png on every page load. I tend to agree with the idea that Gemini should not be extended, as there's always HTTP+HTML for that.
I kind of agree with him, despite being of the opinion that optional inline images should be allowed by the spec. Fetching favicons is going a bit too far for my tastes.
I definitely see situations where Gemini wants to be as bandwidth-friendly as possible, and certain clients auto-downloading resources from the same server would make it difficult to estimate costs/resources/etc.
However for external images available over http/s, I think that should be up to the client.
