1.If you have not set image size from the default settings  /the Automatic resize option off/ you can resize it manually . When you are in "Object editing" stage, select the image and resize it with the control frame that appears around it.

2.If the images are small try not to over resize them - stretching more than 120%  in most cases influenses their quality.

3.It is recommended not to upload extra large files /e.g 2 or 3 times bigger than you will actually need / and resize them afterwards because the system stores their original format in "Directory Browser", and sometimes this may cause runtime errors or slow loading of your website.

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