PicMonkey

Spoonflower has an photo editing link with PicMonkey.  What I like about PicMonkey is its cropping tool and all the resizing options for an image.  There are also different filters that can be applied to the images that are uploaded to PicMonkey.  There are a lot of options with PicMonkey.  It's a site worth exploring and it is simple to use.

For instance, I've been working on a design called "Kitchen Tile."  I first drew, scanned and uploaded my design to Spoonflower:

Original drawing -- you can still see some of the edges surrounding the design.

Same design uploaded to PicMonkey through Spoonflower, enhanced.

Once I got the effect I wanted, my design was downloaded back to Spoonflower.  Spoonflower has options for how a designer wants their design to look on the fabric: centered, basic repeat, half drop, half brick, and mirror repeat.  Choose which option works best for your work and then click "Save this view."