What about some of the african lake synodontis cats? most of those I think would be comfortable in your tank either single or as a trio. They come in a wide variety of colors, personaly I like them better then pictus. and they should be fine with your senegel. Or am I wrong? they can run from 5$-50$ a fish around here generally. I had an adult decorus that was very active and a rather inquisitive/friendly fish when I was growing up in a 55.