Copyright is usually a vague topic on wikis. Most images are allowed as long as the correct license is selected and it is better if the image is credited. Fandom staff can delete images but they usually do that only on request.
On your own wiki, it's really a grey area. Some DeviantArt artists don't like their images used on other websites, and you should at least ask those artists first. There are also artists that like their image to be credited, and there are artists whose images you can freely use. My advise here would be to ask the creator of the images you want to use for permission.