Nowadays the number of people doing SEO pretty much, they compete for the keywords with quality content and backlinks but quite not care about the quality of images. However, If you get high rankings with your images on search engines then it is one of the sources that bring more traffic to your site.
Some SEO factors to make your wallpaper website get better rankings on SEs:
Format and size: One thing to be noted when you create the image that is used for quality .jpg format as well, litmit to us with .png format because with with .jpg then your site is more optimal in terms of download speed, which is one of the important factors in assessing the rankings. Besides the format for images, do not use the image size is too large also affect the speed of loading web pages, you can use some online image tools like Gtmetrix or Pagespeed to optimize your images.
Images name: Pay attention to the image name. This factor plays an important role as the optimal Url for an article, you also need to name photos with keywords to increase capability compete with other images on search results.
Add caption: The use caption of images help to easily identify the content that you want to describe for that image, so you need a clear description of the image content and at the same time containing the keywords you need SEO. Also, if you use unreasonable caption it also affects the bounce rate, if it's not relevant then the users can press the back button immediately is pretty high.
Title and Alt: Want to get high ranking for the image, the title/alt for the picture is as important as what you named for the title of an article. Put with the keywords, no need to put exactly as caption named, you can change according to the context.
Position of images: you need to pay to the content around the image because Google would review the content around the image as the relationship between images and content or not. Therefore, you should pay attention to this factor to put your image for better ranking on search engines...
Hope that helps!