While Magma itself does not provide a dedicated texture node, you can still feed in mapping information into Magma, or evaluate a texture on the particles based on Magma-generated channels.
The way this works is via the dedicated Apply Texture node which was available even before we added Magma to KMY:
In the Krakatoa Modifiers Editor, you can add an Apply Texture node and let it write to any (even custom) channel you would like. Then in Magma, simply add an InputChannel reading the same channel name, and the texture will be passed into the Magma flow.
You can see an example of this in this video, around time 2:20:
If your texture requires UV coordinates, you can use a Magma BEFORE the Apply Texture to generate them. Then the Apply Texture will evaluate the texture per particle based on the Magma channels, and output data that can go directly into Color, Density or whatever, or into another Magma to drive something else. This was used in the Environment Reflection example in this webinar video:
This is similar to generating UVs from Magma in KMX, and then assigning a Diffuse Map to a 3ds Max Standard Material to generate colors for particles under Magma control.