Making a seamless pattern for things like fabric, wallpaper backgrounds or scrapbook paper seems confusing and daunting, but it's actually incredibly easy when you get the hang of it! I've been working on a lot of patterns lately for various projects and thought I'd share how I'm doing it in case anyone else is interested :) I use photoshop to make my patterns, but if you don't have the software there's a neat computer-free tutorial on Design Sponge.
To begin, draw your design on a piece of paper. Make sure none of the lines are touching the edge! Then scan the drawing into your computer. (I use an Epson Perfection V30 scanner.)
Open the drawing in photoshop. Go to Image > Image Size and write down the pixel size. My drawing was 2000 x 2400. Then go to Filter > Other > Offset. Select "Wrap Around." Divide the image size in half, and enter those numbers. So mine would be 1000 and 1200.
(I know I'm absolutely pitiful at explaining how to do things in photoshop so I put a screencast of all the photoshop steps at the end of this post. So if something I say makes no sense whatsoever, watch the video and that should help lol...)
Print your adjusted drawing and layer tracing paper on top. Fill in the big white spaces in the middle to create a seamless design. Once again, make sure that none of your lines go to the edge of the paper! Once you're happy with it, scan your new drawing.
Open it in photoshop, and delete the background. Then copy and paste the image onto the first scan, layering it on top to create the seamless pattern. Flatten the image (Layer > Flatten Image)
At this point, if you're uploading the design to a site like Spoonflower, this is the image you would use. They will automatically tile it for you! Neat-o!
But I also wanted to be able to tile my pattern for use on things like scrapbook paper or society 6 iphone cases without having to copy + paste the image and line it up over and over and over again. In order to do this, go to Edit > Define Pattern. Name your new pattern.
Create a new document. I made a 1000 x 1000px document at 300dpi. Make a new layer (Layer > New > Layer), fill the layer with any color.. it doesn't matter which one you choose (Edit > Fill) then go to Layer > Layer Style > Blending Options and select Pattern Overlay. In the drop down menu, you should see the pattern that you created! Clicking on it will generate a seamless repeat in your new document. You can adjust the size of the pattern by changing the scale.
And that's it! Now here is my photoshop screencast since I'm sure none of the things I just wrote made any sense whatsoever if you're not super familiar with photoshop (or even if you are... I'm just that bad at explaining stuff.)
ps. If you like the design I created in this tutorial, it's available in my society6 shop here and my spoonflower shop here.
pss. I really hope this tutorial will be helpful, but lately (2 years later) I've been receiving a lot of questions asking for extra help. I have a full-time job and this was only supposed to be a fun little post on my blog in case anyone was curious about how I did my own patterns. If you need extra assistance please google other tutorials or you can ask for photoshop help from someone more qualified to assist you.