Creating a pattern using elements designed by yourself

You could make it a brush. 

In Brush Settings set some size and angle jitter, or perhaps set size jitter to pen pressure.

Give it scatter jitter and check Both axis.

Ajust spacing as required.

I also gave it foreground/background and hue jitter and set the colours to something bright.

Those settings gave me this:

You could give it some order by stroking a path with that same brush

Please provide at least one of the images. 

Do the images contain Layers and transparency? 

What »border« do you mean – edges of elements in the image or the edges of the image as a whole? 

Terminology nitpicking:

What’s not represented in the Toolbar is not called a Tool in Photoshop.