Visual metaphors of climate change (e.g., melting glaciers depicted as a melting ice grenade) are regarded as valuable tools for addressing the complexity of environmental challenges. However, few studies have examined their impact on communication, also due to scattered availability of material. Here, we present a novel database of Metaphors of Climate Change in Images (MetaClimage) https://doi.org/10.5281/zenodo.15861012, paired with literal images and enriched with human ratings. For each image, we collected values of difficulty, efficacy, artistic quality, and emotional arousal from human rating, as well as number of tags generated by participants to summarize the message. Semantic and emotion variables were further derived from the tags via Natural Language Processing. Visual metaphors were rated as more difficult to understand, yet more aesthetically pleasant than literal images, but did not differ in efficacy and arousal. The latter for visual metaphors, however, was higher in participants with higher Need For Cognition. Furthermore, visual metaphors received more tags, often referring to entities not depicted in the image, and elicited words with more positive valence and greater dominance than literal images. These results evidence the greater cognitive load of visual metaphors, which nevertheless might induce positive effects such as deeper cognitive elaboration and abstraction compared to literal stimuli. Furthermore, while they are not deemed as more effective and arousing, visual metaphors seem to generate superior aesthetic appreciation and a more positively valenced experience. Overall, this study contributes to understanding the impact of visual metaphors of climate change both by offering a database for future research and by elucidating a cost-benefit trade-off to take into account when shaping environmental communication.