The uploaded image dimensions affect sharpness, but they don't control how large the marker appears on the map. StoreRocket uses the Marker Size selected for your project.
Change how large the marker appears
Go to Widget Settings
Find Marker Size
Choose Extra Small, Small, Medium, Large, or Extra Large
Save and check the live store locator
This setting applies to every custom marker in the project. Uploading a larger source file won't make the displayed marker larger.
Recommended image setup
Use a PNG with a transparent background or an SVG
Keep the file under 1MB
Use a square canvas
Make the artwork fill most of the canvas
Keep the design simple enough to recognize on a map
Large transparent margins make the visible artwork look smaller. Keep only enough space to prevent the design from touching the edge.
For uploading, assigning, and setting default markers, see Custom Map Markers: Upload, Sizing, and Assignment.