How can I add a logo to PCB with Altium Designer?
If you have your logo in vector form, you should export it as dxf which Altium can import. Might not work well with pictures, but since most Logos also come in "simplified" vector forms, it might still be an option.

The procedure of creating a "solid" logo from the DXF lines is a bit lengthy, but very reliable and gives high quality results. Here it is:


Import your dxf file (File>Import>DXF). Choose the correct units.
Use the Inspector panel to set the line width of the DXF geometry to a very small value, e.g. 1 mil
Draw a polygon pour around the shape (Place>Polygon pour), select pour over same net objects and disable removal of Islands. Set small values for neck width and arc approximation.
Adjust the clearance for the polygon to the DXF lines to 0 by adding a specific design rule
Repour the polygon, then select it, right click on it and use Polygon Actions>Explode selected Polygons to Free Primitives
Now your polygon consists of several copper regions. You can delete all regions that should not be filled, as well as your original DXF lines.
Group your regions by selecting them and creating a union from them (Tools>Convert>Create Union from selected objects).


This approach works best if you put your logo into a PCB library, so you can simply place it on any PCB and edit it at a central location.

There is also an official Altium Video explaining this process.