Start with Kodi/DBMC>System (click it!)>Appearance>
For turning the RSS feed off/on/changing the actual feed, see last two visible items on screen now)
For changing the wallpaper, head to same area, but click
Settings (2nd line down, under Skin)>Background Options
Under the background section, turn on "Enable customer background", then the line below won't be greyed out. You can now navigate through your device's file system and locate the image you want to have as the wallpaper for Kodi.
Sticking with Confluence is my personal preference for a skin, and changing the wallpaper (unless you're going to use a very high resolution, non-optimized image) will have a negligible effect on your RAM. In most cases, a few hundred kilobytes at most I would think.