MTP Tile Maker is a free windows program that will mirror .png image to the bottom and side creating a simple collide-scope effect. Press anywhere on the window an you can load an image. Use the flip joystick to change image orientation. Use the zoom joystick to cover seams making it tiled.
Check all four angles with flip to see if there are any seams. Use Edge to fine tune any seams away. Always zoom down and to the left to make sure you have enough room to edge out the seams. Press the space bar to save the image. The location of the save is in the instructions when you first start the program(make a short cut on your desk top). Name the file as you wish and press enter. The resolution of the images will match your desktop. Click on the window to choose another picture. Press ESC to end the program.
Made with AppGameKit I use it for titles, backgrounds, and to make seamless tiles. Very simple but useful.
Have fun!
MTPollard
https://chromatic3d.itch.io/mtp-tile-maker