These 2 lines indicate that you want all of <img> elements in the page to be checked. Naively you assume that the keyword WebUI.veirfyAllLinksOnCurrentPageAccessible includes <img> elements. But I doubt it.
Though I am not sure. The documentation does not tell if the keyword includes <img> or not. How about checking the source code? The verifyAllLinksOnCurrentPageAccessible keyword’s source is published at
https://github.com/katalon-studio/katalon-studio-testing-framework/blob/master/Include/scripts/groovy/com/kms/katalon/core/webui/keyword/builtin/VerifyAllLinksOnCurrentPageAccessibleKeyword.groovy. However I could not find the source code portion which tells if the keyword checks <img> elements or not. It seems that the portion is unpublished. I have got no clue.