There is a really cool free app called PicsArt that you can use to make cool covers for your instructables. I am not affiliated with them, but i did think it was worth recommending. It works on iphone and android. No copyright infringement intended... Just a cool app.
Step 1: App Store
Go to the app store
Step 2: Search PicsArt
Type PicsArt into the search bar. Click the first app. Download it for free.
Step 3: Open
Wait for the app to load and then open it.
Step 4: Main Menu
On the main menu, click "photo."
Step 5: Gallery
Click on "gallery" and choose a picture. It will show up on a board.
Step 6: Add Text
To add text click the "add" button then the "text" (A) button.
Step 7: Word
Type a single word and adjust the font style and colors.
Step 8: Locate
Locate the word on the picture and move/scale it. Click the checkmark when done.
Step 9: Crop
If you want you can crop the picture to fit the instructables screen. Click the bottom left button and "crop." Click checkmark when done.
Step 10: Check
Make shure you like youre picture!
Step 11: Save
Click the center top button to save.
Step 12: Done!!!
You're done!!! Sorry if i was a bit laconic, but it WAS a lot of typing... Enjoy! I made my logo on PicsArt too! No copyright infringement intended!!!