How to Make a Seamless Repeating Pattern in Photoshop
You’ll build a square pattern tile, arrange clip art or illustrations, and use the Offset filter to align edges for a seamless repeat. After refining the center, you’ll define the tile as a pattern and test the result with Edit → Fill.

Step-by-step instructions
Create a new square document
Go to File → New.
Set Width: 400 px, Height: 400 px, Resolution: 72 ppi.
Set Color Mode: RGB, Background Contents: White.
Click Create.
Set a custom background color
In Layers, click the lock on the Background layer to unlock it.
Set your foreground color (e.g., a light pink), then fill via Edit → Fill → Contents: Foreground Color (or use the Paint Bucket).
Click the lock icon again to relock the background.
Place and arrange your artwork
Drag your clip art/graphics into Photoshop.
Use Edit → Free Transform (Ctrl/Cmd+T) to scale/rotate, then click the checkmark.
Repeat to add more elements; use the Move Tool (V) with Auto-Select enabled to position items.
Merge the design layers
Shift-click to select all artwork layers in the Layers panel.
Right-click → Merge Layers to combine them.
Offset to create seamless edges
Go to Filter → Other → Offset.
Set Horizontal: 200 px and Vertical: 200 px (half the tile size).
Ensure Wrap Around is selected, then click OK.
Fill the center and refine
Add more elements in the central empty area to balance the design.
Use Edit → Transform → Flip Horizontal (or rotate) on elements for variation.
Reposition/scale as needed, then merge the design layers again (right-click → Merge Layers).
Define and test the pattern
Go to Edit → Define Pattern, name it, and click OK.
Create a new, larger document.
Choose Edit → Fill → Contents: Pattern, pick your new pattern, and click OK to test the seamless repeat.