If you try to upload images from your PC directly by media picker in the RTE, they wouldn't appear in the RTE box until you save or publish the node.
Note that if you pick images from your current gallery, they would appear.
I am seeing this issue on Umbraco version: 8.6RC
Fresh Umbraco 8.6 RC installation
1- Create RTE property in any existing node
2- Upload images directly form your PC
3- Click Save or Save & Publish to be able to see the uploaded images in the RTE box

I expect to see the uploaded images in the RTE box
Uploaded images didn't appear
_This item has been added to our backlog AB#5516_
@saifobeidat hmmm I recall having fixed something along those lines at some point 馃 and I don't see this bug in the latest v8/contrib.
The media picker should display a new dialog subsequent to picking the uploaded image, but in your GIF it does not - it just closes. Are there any JS errors in the console?
I can reproduce, will have a look at the history of v8/contrib - the image is selected after upload, but it doesn't "actually" seem selected.
Looks like this would've fixed it, but it's not working any more: https://github.com/umbraco/Umbraco-CMS/pull/6995
@nul800sebastiaan I believe it wasn't working even before, as it was stated in Musab's comment
For the life of me I still can't reproduce this in v8/contrib. Is anyone seeing any console errors?
@kjac yes there is an error appears on the console :
http://localhost:64649/nothing.jpg 404 (Not Found)
it appears when I click "select" button, and appears again when I publish the node
Hmmmmm well I still can't reproduce on vLatest, but now at least I can see an error in the console:

Looks like a bad merge has removed a dependency in the media picker controller. When I re-introduce that dependency I can reproduce the bug y'all are seeing.
I've got a PR incoming 馃憤
PR in #7745
@kjac this the version that I downloaded and has the issue: https://our.umbraco.com/download/releases/860 I don't know if it's the same as latest v8/contrib
@saifobeidat That's not the same. This issue has now been fixed for the upcoming final release of 8.6.0 (due out next week).