The Alternanthera reineckii 'Mini' is an nice red plant that can grow up to +- 35 - 40 centimeters.
Bacopa caroliniana originates from US, stems become 10-30 cm long and 3-4 cm wide. Apart from relatively good light it makes few demands.
Dwarf Needle Grass (Eleocharis acicularis 'Mini') is as the name suggests, a grass plant for the aquarium. Gets +- 5 centimeters high.
Glossostigma elatinoides from New Zealand is much in demand in aquariums. It is one of the smallest aquarium plants, and thus a good foreground plant. Gets +- 2-3 centimeters high.