Currently, Starter plan users can upload 5 images into the gallery.
Should you wish to add more, then the Basic, Plus, and Reputation plans offer unlimited photo additions.
The maximum size that an image can have is 25MB.
Please use one of the following formats: bmp, gif, jpe, jpeg, jpg, png, tif, tiff.
UENI recommends the following resolutions:
Logo, minimum size 200x200px
Hero image (big banner image at the top of your website), minimum size 1900x500px
Gallery images, minimum size 1024x300px
If you have a Windows operating system, then you can try using this third-party tool to resize your images. Click Here.