MAKE YOUR OWN SEAMLESS PATTERN

Making seamless patterns from illustrations is a pretty useful trick. There are many ways to make a repeat pattern, but my favorite (& the most easiest way, according to me) is using Photoshop! Here's how I made this one.
First, obviously, I scanned the drawing and imported in to Photoshop & make any adjustments (color, brightness, contrast etc. if needed). After that I duplicated the layer (turning off the original layer which will make up the center of the pattern eventually) & using the selection tool I cut the drawing into half and swapped it to either side like below.

 Again, I split the drawing into half and flipped it over, moving each half to top & bottom corner.

At this point I turned on the original drawing layer, to check the composition.

 And added a few more details to fill in the blank white space. That's it! Repeat pattern ready...!