Looks like you're missing most, if not all of the game's textures. The best course of action here is to try re-installing the game. Here are the quick Steam re-install steps for Windows users. Please give them a try.

1. Right-click Spiral Knights in the Steam Library and choose the "Delete Local Content" option to remove the game.
2. Navigate to your Steam Spiral Knights folder (default C:\Program Files (x86)\Steam\steamapps\common\spiral knights) and delete any remaining files or folders.
3. Go to Spiral Knights in the Steam Store and install the game again normally. The game will automatically patch to the current version when launched.