RPGuild itself has an image hosting feature. If you go to your profile, it's under this tab:

[img]https://img.roleplayerguild.com/prod/users/01999a72-d136-741d-80c8-cef95d242bfb.webp[/img]

(The Images one, obviously.)

Otherwise, I have no idea what a good alternative would be. Imgur's all I've used for the last decade and some change.