You can probably have whatever texture the part needs to function correctly. The texture is applied to the mould tool prior to use and that can be done in different ways. Sand or bead blasting can be used. In fact bead blast is the main chosen route with aluminium tooling. Spark erosion is very common, particularly in economy tooling programmes, as it is often part of the tool manufacture process anyway. A full DIN standard erosion chart/stick can be obtained from good engineering supply companies, the machine manufacturers, or sourced on the web at quite low cost. Chemical etching is also used commonly, particularly where special patterning is required, or an easy-clean texture needed. So this is often employed on higher-volume projects as with vehicle manufacturers. Again, the process suppliers (Moldtec and others) will have moulded sample books with hundreds of different patterns for selection. Don't forget that whatever you use, you will need to apply appropriate draft angles to the mould faces, sufficient to avoid hang-up in the texture depth. So that will vary according to the choice.