Never use Minitokyo as a source. While Konachan WAS initially created because some people disliked Minitokyo's team, it has long since been deprecated due to the poor quality wallpaper being uploaded (and those GOD AWFUL WATERMARKS left by the morons who edit images into wallpapers).
And yes, it's hard to upload something when others are active through Pixiv/Danbooru. If you have the time, you can lurk Pixiv and Danbooru to snatch the uploadable image and do it. Otherwise you'll have to get crafty and check out every image that you might think it's not here. Popular titles are targeted more so than others because of the high amount of fan art that they bring.