Can I add images as 'input' of the calculator (different images to choose from)?

Yes, there is an advanced field type (Pro plan only) called 'image selector'. The configuration is simple: you set at the spreadsheet the list of the urls for the images, and at the input field you type the range where to find them, for ex : B4:B8 This will create an image selector with 4 images, according to the 4 urls provided at that range.