I sometimes take a photo with my "Quadrant Kaleidoscope effect" in mind, or view an older photo, or someone else's photo. The image is imported into GIMP as a layer. The canvas is increased 200%, both vertical and horizontal. Make 3 copies of the layer, you now have 4 layers in the upper left corner. Using the move tool, choose a layer and move each layer to an approximate new corner - leave the original image anchored in the upper left corner. When moving a layer, I also rename each layer with 1,2,3, and 4, for later ease of manipulation, 2 is upper right, 3 is lower left, 4 is lower right, and the original image is 1, upper left. In the layer box, Grab the bottom layer (now number 1) and drag it to the top of the layers. You should have 1,2,3,4 in order, matching the clockwise 4 corners of the canvas. Use the move tool again, with mouse and arrow keys to carefully join layers 2, 3, and 4, to the anchored layer 1, upper left image. Then, choose one layer at a time, and use the flip tool (horizontal and/or vertical) to change the images to get the quadrant kaleidoscope image you want. You will have 4 different ways to explore. At the end, I export as a JPEG image, with detail in the 3 to 4 meg file size. Have fun.