Rounded Corners
It is very simple to make layouts with rounded corners in MS Paint. Here's what you do:
Step 1: Start by finding a picture you like and then open it in Paint. Here's the picture I've choosen to use:
Step 2: Then select the
Line tool, which looks like this:

. Choose the thickest line and then select the
Rounded rectangle tool, which looks like this:
Step 3: Make the color white and then make a Rectangle around the picture where you want it. Here's how mine looks now:
Step 4: Now you have to use the
Paint brush tool, which looks like this:

, then select the color white and start painting around the lines, where you can still see parts of the image.
Step 5: When it is all white, you're done! If you want to make it transparent, you can download a program called 'GIFFY' (it is free) and then you can make it transparent there. I've put out a tutorial on how to do it. Here's my finished rounded corner layout: