Technically, African Violets are not great companion plants to Phalaenopsis.
Here's why. To bloom African Violets for a long time without pause, you have to make sure the temperature does not go above 28C, I think that's around 80F. Plants will be fine, but it is already too hot for them and they will not flower until cooler condition returns.
If you don't mind flowerless violets for months, then this is not a problem.
If you keep AV under too cool a temperature, they will also not flower.
Phalaenopsis on the other hand grows the best and fastest during the hot and humid conditions, in temperate zone, this is during the short late spring into summer months when they do most of their growing.
They will still grow fine under not so hot conditions, but I'm just pointing out the ideal growing and flowering conditions to clarify.
With that said, vast majority of commonly sold houseplants will be happy where phalaenopsis are happy.
It's a matter of your taste in plant size, appearances, colors, shapes, ....as there are just way too many to choose from.
Begonias are good one, although certain ones like tuberous begonia with large showy flowers do not like temperature as warm as phalaenopsis, and don't tolerate lower humidity that phalaenopsis won't have issue with.
Streptocarpus is a good one in that they can be grown along side African Violet and have lots of colors to choose from.
Are you looking for non-orchids only??
Many other orchids will grow perfectly fine where phalaenopsis grows and flower well.
Many paphiopedilums, oncidiums, cattleyas, even vandas and dendrobiums depending on how you care for your phalaenopsis.
Can you be more specific about your growing conditions so others can better help you?
Where are you phals? which exposure? Are their any tall trees or buildings blocking the sun?
How well do you do with your phalaenopsis?