Depends on which ones exactly you wanna overwrite. If it's just for this menu you can do that in the 'Options' Tab by playing them in a specific path, adding this path to the list and removing the others.
If you want them to show during a Mapvote you'll have to add that path to the !mvmenu>Map Preview Hierarchy and place it at the top

If I wanted to use my own custom icons exlusively - or at least make them always overwrite the ones from the central hub - where would I place the screenshots? An is there anything else to configure?

Ohh. Well anyway, it should be working fine now. I tested it with a fresh installation

gmod update not this things updates

Oh yeah. Now you say it, I'll switch the base folder to a different one to prevent conflicts with the old files before rework

nvm I think these errors are due to the new update that's fucked everything up lol

+fixed
I forgot to correctly create the base file directory /data/mapicon

Nope fresh install I just get a ton of issues in general

Have you edited the map preview hierarchy file manually?

[Super Map Icon Maker] lua/autorun/client/cl_icon_maker.lua:693: bad argument #1 to 'ipairs' (table expected, got string)
1. ipairs - [C]:-1
2. createBrowser - lua/autorun/client/cl_icon_maker.lua:693
3. unknown - lua/autorun/client/cl_icon_maker.lua:1034
4. unknown - lua/dlib/modules/hook.lua:904
got this opening menu trying to do anything

+fixed

[Super Map Icon Maker] lua/autorun/client/cl_icon_maker.lua:36: bad argument #1 to 'ipairs' (table expected, got boolean)
1. ipairs - [C]:-1
2. loadNextMap - lua/autorun/client/cl_icon_maker.lua:36
3. DoClick - lua/autorun/client/cl_icon_maker.lua:979
4. unknown - lua/vgui/dlabel.lua:253

I just reworked the entire addon. Try the new chat command !smm for the GUI.
If you wanna share your map thumbnails/icons with others I recommend making a map icon pack, copy the map icons and publish it on the workshop

sorry typo, i've also put the screenshots into my /data/mapicon/ folder and did mapicon_pushMapIconsToServer. when i type in mapicon_filebrowser it says unknown command.

Please refer to the 'How do I upload the screenshots that I've made to the server?' section. The console command is mapicon_filebrowser

takes the screenshots but not sure how i can get them into the server and connecting to all clients, trying to do this for map icons to show up on a map vote i'm using, i've tried mapicon_syncPlayerMapIconsWithServer and mapicon_pushMapIconsToServer but they both don't seem to work, i try to type in map_filebrowser but that doesn't seem do anything.

I've updated the addon. Please check if it's working now

mapicon_syncPlayerMapIconsWithServer 0
doesn't work, it still sends files to clients

+fixed
Issue was a recent update to Gmod that blocked render capture functions while main menu was open

Same issue Laci Angel described is happening to me too now. The pictures are 0 Bytes.

+done

to be clear i referring to map icons that aren't generated by this addon

That should be possible. I'll take a look

Do you think you could an option to ignore icons from the maps files. I've noticed on my server if my clients don't have the map download they can't see the icons of the maps.

+found some kind of workaround through pm

Do you get any errors in your console?

It was originally. I changed the code so that the viewmodel is disabled when a screenshot is captured

I assumed it was intentional to avoid the viewmodel render in the preview ( you can see it when you look down)

Thank you for reporting. It should be fixed now

Do you think you'll can an option to change the height of the camera I've noticed it's offset a bit from the player view

There's a limit to how big data can be to be send to the server. 3000 maps seem to be too much. I might add a compression to it to fix that

3000 maps?! oh lord

Ok, so I semi fixed my issue. I clean reinstalled my GMOD, and moved all but 500 of my maps so GMOD couldn't see them. Turns out this addon doesn't like when you have ~3000 maps in your game's folder at one time.

I forgot to actually show the error message, my bad

[EASY Map Icon Maker + Automatic Server/Client Synchronization] Trying to send an overflowed net message!
1. func - lua/autorun/server/sv_icon_maker.lua:182
2. unknown - lua/includes/extensions/net.lua:38

I'll take a look

Ive been getting a lot of errors that say "Host_Error: Reliable message (type 23) discarded." whenever I use the mapicon_screenshot command. Any idea what's wrong?

holy crap why this isnt on the top of the workshop

Thanks

+fixed
Thanks for reporting!

[ERROR] lua/autorun/client/cl_icon_maker.lua:218: attempt to index a nil value
1. fn - lua/autorun/client/cl_icon_maker.lua:218
2. unknown - lua/ulib/shared/hook.lua:109