Today I created a new background image for my blog, and I decided to create a tutorial along the way. I have adapted this method of making repeating pattern tiles from information I've found at a variety of sources, so none of this reinvents the wheel, but it is my own little method that might help some other folks get into pattern design.
Full tutorial after the jump:
Materials & tools needed:
A few sheets of drawing paper that can go through your printer
Drawing tools of your choice (I used pencils)
Step 1. Begin by drawing a portion of your motif. Above you can see my beginning. Make sure not to draw anything that goes off the edge of your paper.
Step 2. Scan your design into Photoshop and clean up the linework however you'd like. (I always use Curves to bump up the contrast, select the linework with the Wand tool, then create a new layer where I use the paint bucket to fill in the linework selection with my chosen color, in this case green.)
Size the image the way you'd like (for Spoonflower, for instance, create the image at the size you like at 150 dpi) and write down how many pixels wide and tall your image is.
Once your scanned image is all set, choose "Offset" under the Filter menu. Starting with either horizontal or vertical (or both if you prefer—just play around with it to see how you like to work), set the offset to one half the number of pixels of your image. (My image is 800 pixels wide, so I started with a vertical offset of 400 pixels.) Make sure the "Wrap Around" radio button is selected. This is what will allow the image to pop up on the other side of your file.
Step 3. Print out your offset design onto a sheet of your drawing paper.
See the gap between the top and the bottom of the design in Step 2? In step 3, you'll want to fill that in with more drawing. In the Step 3 photo, you can see the printout in bright pink and the new pencil lines in gray. I'm just drawing more bits of my design to connect the top and bottom of the design.
Step 4. Scan your Step 3 drawing into Photoshop. Copy the new drawing into your first file as a new layer. Line up the two motifs. (If you kept the white background of your first drawing, you can set the layer to "Multiply" in the Layer menu to see what's underneath.)
In the layer with your Step 3 drawing, erase everything that was in the printout. In the above photo, I erased all the green portions of the new drawing layer to ensure that I didn't have any image doubling due to imperfectly aligned layers.
You'll want to keep the original image (instead of just using the new scanned image) because it will be so much easier to align the edges in the end. If you try to use the image you just scanned in, you will have to make some corrections to the file to ensure that the edges aligned perfectly. It's much easier to use the edges that Photoshop created when you used the Offset filter.
Step 5. Merge together the two layers you worked with in the previous step. Then, select the Offset filter again, but this time, offset in the other dimension. (I offset vertically first, so now I offset horizontally.)
From this point forward, you will just repeat the previous steps. Print out this offset, draw more portions of your design (always keeping away from the edge of the paper), scan, align, and merge with your previous work.
It's also a good idea at this point to start testing your design to see if anything needs to be adjusted. You can see that I've done this by setting my desktop background to be a tiled version of my Photoshop file.
Step 6. Keep repeating the previous steps until your entire tile is covered to your liking. I find I usually have one little corner left to do at the end, so the above photo shows me filling in that last little empty spot.
Step 7. Once you have your linework done, you can start coloring. You will still want to stay away from the edges of your design to keep a nice flow to your work. Color in the middle section of your design, then use the Offset filter to get the edges into the center to work on them, too. If you keep your linework and color in separate layers, you'll need to offset each layer individually.
Keep coloring and offsetting until your tile is complete.
Step 8. Admire your hard work!
If you have any questions whatsoever, let me know in the comments, and I'll do my best to make everything crystal clear.