Advice for planter

hello, I have two planter 12 inches square and 16 inches deep. Have pot to go inside. They are in a conservatory that has shading in summer as it is facing south west, but a mesh screen door for hot days.. No heating in winter except it’s on the side of the house. I have had orange and a lemon tree in there growing to 4 feet. Excellent , evergreen, wonderful perfume, fruit and glossy leaves. Only trouble was they liked to be outside for the summer and I could not lift them, so scale and mold was a major problem. 
I need a few suggestions please on what to buy to give  me a year round display. I would appreciate any suggestions especially if they have the same attributes  as the citrus trees. Many thanks Val