NO GOOD. The plugin saves tag image into OPTIONS table.

You should re-think the way you save your plugin’s data. As of right now, it saves term image link into the options table, which is no good. A site may have hundreds of term images, which will bloat the options table. Every time any script needs to get an option, which is all the time, the server will have to go through all the data from your plugin. It may slow down a site considerably. To save additional data from a term, there’s a table called termmeta, I think a link to term image belongs there.