Why are certain images accepted more quickly than others?

Adobe Stock receives thousands of submissions per week.

Review times vary based on how many assets were ahead of yours in the wait queue and the type of assets you submitted. 

24 hours is very rare. Most assets take 5-15 business days.  Illustrations and Generative AI could take 1-3 months.

What kind of images and do they have releases attached? Generally, Adobe pretends that assets are getting moderated on a first in, first out basis. However, it may be that this is not an absolute rule, and it may also be that they are experimenting sporadically with methods to get assets moderated faster.

However, submitting different kinds of assets (photos, illustrations, vectors, videos, …) will lead to different waiting times.

Welcome to the Community Forum; looks like you're new here. Peruse other recent posts and you'll learn that review delay is a frequent discussion topic. Due to the huge influx of generative AI assets from contributors uploading hundreds at a time, review time has grown to 2 months or more for such assets. Other asset types are being reviewed in a more reasonable period f time. What asset type did you submit?