Caladiums are often grown as an annual in climates where they will not survive the winter (which is almost everywhere).

Since I assume your 'plan' is suggesting a splash of color in a somewhat shady garden, you could substitute coleus if you are intent on sticking to the plan and using a colorful foliage. I can't think of any hardy perennial plant that will fit that description.

Are you looking at a general plan, or one that was specifically drawn for your garden? Does the plant or leaf size matter if the general colors are correct - or can the leaf be of a different color as long as the approximate size is adhered to? Caladiums are rather unique in color and size -- If rhizo_1 can't come up with a suggestion, then there probably aren't any good substitutions! (All I can think of is houttaneyia, which has colors but not size!)

Almost everyone who has caladiums, grows them as the very tender plant they are. The sizes and colors available are wonderful. You can buy the little tubers and start them inside (I start them in early March for zone 6b); use very well drained soil, keep the air warm, and put them in a bright window. Keep slightly moist but never saturated. They take almost as long as cannas to sprout (a lo-o-ong, lo-o-ong couple months). Once planted, don't let even the sprouts get chilly. When your weather has warmed enough that even nighttime lows stay above 60*F, they can be planted outside. In my experience, they have zero tolerance for chills, and the first frosty night will wipe them out -including ruining the tuber. If you have a basement, cellar, or attic that remains well above frost-temperatures, you can overwinter the tubers the same as for cannas or dahlias. IMO, they are easier to maintain if permanently planted in pots (not too deep and with superb drainage) and just bring the pots in for overwinter -- if kept warm enough, they just might keep on growing all winter.

Here is a link that might be useful: caladium advice